beta-secretase 1 isoform G [Homo sapiens]
Protein Classification
pepsin/retropepsin-like aspartic protease family protein( domain architecture ID 27721)
pepsin/retropepsin-like aspartic protease family protein
List of domain hits
| Name | Accession | Description | Interval | E-value | ||||
| pepsin_retropepsin_like super family | cl11403 | Cellular and retroviral pepsin-like aspartate proteases; This family includes both cellular ... |
1-203 | 5.98e-152 | ||||
Cellular and retroviral pepsin-like aspartate proteases; This family includes both cellular and retroviral pepsin-like aspartate proteases. The cellular pepsin and pepsin-like enzymes are twice as long as their retroviral counterparts. The cellular pepsin-like aspartic proteases are found in mammals, plants, fungi and bacteria. These well known and extensively characterized enzymes include pepsins, chymosin, rennin, cathepsins, and fungal aspartic proteases. Several have long been known to be medically (rennin, cathepsin D and E, pepsin) or commercially (chymosin) important. The eukaryotic pepsin-like proteases contain two domains possessing similar topological features. The N- and C-terminal domains, although structurally related by a 2-fold axis, have only limited sequence homology except in the vicinity of the active site. This suggests that the enzymes evolved by an ancient duplication event. The eukaryotic pepsin-like proteases have two active site ASP residues with each N- and C-terminal lobe contributing one residue. While the fungal and mammalian pepsins are bilobal proteins, retropepsins function as dimers and the monomer resembles structure of the N- or C-terminal domains of eukaryotic enzyme. The active site motif (Asp-Thr/Ser-Gly-Ser) is conserved between the retroviral and eukaryotic proteases and between the N-and C-terminal of eukaryotic pepsin-like proteases. The retropepsin-like family includes pepsin-like aspartate proteases from retroviruses, retrotransposons and retroelements; as well as eukaryotic DNA-damage-inducible proteins (DDIs), and bacterial aspartate peptidases. Retropepsin is synthesized as part of the POL polyprotein that contains an aspartyl-protease, a reverse transcriptase, RNase H, and an integrase. The POL polyprotein undergoes specific enzymatic cleavage to yield the mature proteins. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A) and A2 (retropepsin family). The actual alignment was detected with superfamily member cd05473: Pssm-ID: 472175 [Multi-domain] Cd Length: 364 Bit Score: 428.38 E-value: 5.98e-152
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| Name | Accession | Description | Interval | E-value | ||||
| beta_secretase_like | cd05473 | Beta-secretase, aspartic-acid protease important in the pathogenesis of Alzheimer's disease; ... |
1-203 | 5.98e-152 | ||||
Beta-secretase, aspartic-acid protease important in the pathogenesis of Alzheimer's disease; Beta-secretase also called BACE (beta-site of APP cleaving enzyme) or memapsin-2. Beta-secretase is an aspartic-acid protease important in the pathogenesis of Alzheimer's disease, and in the formation of myelin sheaths in peripheral nerve cells. It cleaves amyloid precursor protein (APP) to reveal the N-terminus of the beta-amyloid peptides. The beta-amyloid peptides are the major components of the amyloid plaques formed in the brain of patients with Alzheimer's disease (AD). Since BACE mediates one of the cleavages responsible for generation of AD, it is regarded as a potential target for pharmacological intervention in AD. Beta-secretase is a member of pepsin family of aspartic proteases. Same as other aspartic proteases, beta-secretase is a bilobal enzyme, each lobe contributing a catalytic Asp residue, with an extended active site cleft localized between the two lobes of the molecule. The N- and C-terminal domains, although structurally related by a 2-fold axis, have only limited sequence homology except the vicinity of the active site. This suggests that the enzymes evolved by an ancient duplication event. The enzymes specifically cleave bonds in peptides which have at least six residues in length with hydrophobic residues in both the P1 and P1' positions. The active site is located at the groove formed by the two lobes, with an extended loop projecting over the cleft to form an 11-residue flap, which encloses substrates and inhibitors in the active site. Specificity is determined by nearest-neighbor hydrophobic residues surrounding the catalytic aspartates, and by three residues in the flap. The enzymes are mostly secreted from cells as inactive proenzymes that activate autocatalytically at acidic pH. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133140 [Multi-domain] Cd Length: 364 Bit Score: 428.38 E-value: 5.98e-152
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| Asp | pfam00026 | Eukaryotic aspartyl protease; Aspartyl (acid) proteases include pepsins, cathepsins, and ... |
2-182 | 3.12e-17 | ||||
Eukaryotic aspartyl protease; Aspartyl (acid) proteases include pepsins, cathepsins, and renins. Two-domain structure, probably arising from ancestral duplication. This family does not include the retroviral nor retrotransposon proteases (pfam00077), which are much smaller and appear to be homologous to a single domain of the eukaryotic asp proteases. Pssm-ID: 394983 [Multi-domain] Cd Length: 313 Bit Score: 79.63 E-value: 3.12e-17
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| Name | Accession | Description | Interval | E-value | ||||
| beta_secretase_like | cd05473 | Beta-secretase, aspartic-acid protease important in the pathogenesis of Alzheimer's disease; ... |
1-203 | 5.98e-152 | ||||
Beta-secretase, aspartic-acid protease important in the pathogenesis of Alzheimer's disease; Beta-secretase also called BACE (beta-site of APP cleaving enzyme) or memapsin-2. Beta-secretase is an aspartic-acid protease important in the pathogenesis of Alzheimer's disease, and in the formation of myelin sheaths in peripheral nerve cells. It cleaves amyloid precursor protein (APP) to reveal the N-terminus of the beta-amyloid peptides. The beta-amyloid peptides are the major components of the amyloid plaques formed in the brain of patients with Alzheimer's disease (AD). Since BACE mediates one of the cleavages responsible for generation of AD, it is regarded as a potential target for pharmacological intervention in AD. Beta-secretase is a member of pepsin family of aspartic proteases. Same as other aspartic proteases, beta-secretase is a bilobal enzyme, each lobe contributing a catalytic Asp residue, with an extended active site cleft localized between the two lobes of the molecule. The N- and C-terminal domains, although structurally related by a 2-fold axis, have only limited sequence homology except the vicinity of the active site. This suggests that the enzymes evolved by an ancient duplication event. The enzymes specifically cleave bonds in peptides which have at least six residues in length with hydrophobic residues in both the P1 and P1' positions. The active site is located at the groove formed by the two lobes, with an extended loop projecting over the cleft to form an 11-residue flap, which encloses substrates and inhibitors in the active site. Specificity is determined by nearest-neighbor hydrophobic residues surrounding the catalytic aspartates, and by three residues in the flap. The enzymes are mostly secreted from cells as inactive proenzymes that activate autocatalytically at acidic pH. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133140 [Multi-domain] Cd Length: 364 Bit Score: 428.38 E-value: 5.98e-152
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| pepsin_like | cd05471 | Pepsin-like aspartic proteases, bilobal enzymes that cleave bonds in peptides at acidic pH; ... |
1-182 | 1.40e-19 | ||||
Pepsin-like aspartic proteases, bilobal enzymes that cleave bonds in peptides at acidic pH; Pepsin-like aspartic proteases are found in mammals, plants, fungi and bacteria. These well known and extensively characterized enzymes include pepsins, chymosin, renin, cathepsins, and fungal aspartic proteases. Several have long been known to be medically (renin, cathepsin D and E, pepsin) or commercially (chymosin) important. Structurally, aspartic proteases are bilobal enzymes, each lobe contributing a catalytic Aspartate residue, with an extended active site cleft localized between the two lobes of the molecule. The N- and C-terminal domains, although structurally related by a 2-fold axis, have only limited sequence homology except the vicinity of the active site. This suggests that the enzymes evolved by an ancient duplication event. Most members of the pepsin family specifically cleave bonds in peptides that are at least six residues in length, with hydrophobic residues in both the P1 and P1' positions. The active site is located at the groove formed by the two lobes, with an extended loop projecting over the cleft to form an 11-residue flap, which encloses substrates and inhibitors in the active site. Specificity is determined by nearest-neighbor hydrophobic residues surrounding the catalytic aspartates, and by three residues in the flap.The enzymes are mostly secreted from cells as inactive proenzymes that activate autocatalytically at acidic pH. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133138 [Multi-domain] Cd Length: 283 Bit Score: 85.55 E-value: 1.40e-19
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| Asp | pfam00026 | Eukaryotic aspartyl protease; Aspartyl (acid) proteases include pepsins, cathepsins, and ... |
2-182 | 3.12e-17 | ||||
Eukaryotic aspartyl protease; Aspartyl (acid) proteases include pepsins, cathepsins, and renins. Two-domain structure, probably arising from ancestral duplication. This family does not include the retroviral nor retrotransposon proteases (pfam00077), which are much smaller and appear to be homologous to a single domain of the eukaryotic asp proteases. Pssm-ID: 394983 [Multi-domain] Cd Length: 313 Bit Score: 79.63 E-value: 3.12e-17
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| cnd41_like | cd05472 | Chloroplast Nucleoids DNA-binding Protease, catalyzes the degradation of ribulose-1, ... |
9-186 | 5.53e-10 | ||||
Chloroplast Nucleoids DNA-binding Protease, catalyzes the degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase; Chloroplast Nucleoids DNA-binding Protease catalyzes the degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in senescent leaves of tobacco. Antisense tobacco with reduced amount of CND41 maintained green leaves and constant protein levels, especially Rubisco. CND41 has DNA-binding as well as aspartic protease activities. The pepsin-like aspartic protease domain is located at the C-terminus of the protein. The enzyme is characterized by having two aspartic protease catalytic site motifs, the Asp-Thr-Gly-Ser in the N-terminal and Asp-Ser-Gly-Ser in the C-terminal region. Aspartic proteases are bilobal enzymes, each lobe contributing a catalytic Asp residue, with an extended active site cleft localized between the two lobes of the molecule. One lobe may be evolved from the other through ancient gene-duplication event. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133139 [Multi-domain] Cd Length: 299 Bit Score: 58.82 E-value: 5.53e-10
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| SAP_like | cd05474 | SAPs, pepsin-like proteinases secreted from pathogens to degrade host proteins; SAPs (Secreted ... |
4-182 | 1.13e-09 | ||||
SAPs, pepsin-like proteinases secreted from pathogens to degrade host proteins; SAPs (Secreted aspartic proteinases) are secreted from a group of pathogenic fungi, predominantly Candida species. They are secreted from the pathogen to degrade host proteins. SAP is one of the most significant extracellular hydrolytic enzymes produced by C. albicans. SAP proteins, encoded by a family of 10 SAP genes. All 10 SAP genes of C. albicans encode preproenzymes, approximately 60 amino acid longer than the mature enzyme, which are processed when transported via the secretory pathway. The mature enzymes contain sequence motifs typical for all aspartyl proteinases, including the two conserved aspartate residues other active site and conserved cysteine residues implicated in the maintenance of the three-dimensional structure. Most Sap proteins contain putative N-glycosylation sites, but it remains to be determined which Sap proteins are glycosylated. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). The overall structure of Sap protein conforms to the classical aspartic proteinase fold typified by pepsin. SAP is a bilobal enzyme, each lobe contributing a catalytic Asp residue, with an extended active site cleft localized between the two lobes of the molecule. One lobe may be evolved from the other through ancient gene-duplication event. More recently evolved enzymes have similar three-dimensional structures, however their amino acid sequences are more divergent except for the conserved catalytic site motif. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133141 [Multi-domain] Cd Length: 295 Bit Score: 57.58 E-value: 1.13e-09
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| Cathepsin_D2 | cd05490 | Cathepsin_D2, pepsin family of proteinases; Cathepsin D is the major aspartic proteinase of ... |
1-182 | 1.58e-09 | ||||
Cathepsin_D2, pepsin family of proteinases; Cathepsin D is the major aspartic proteinase of the lysosomal compartment where it functions in protein catabolism. It is a member of the pepsin family of proteinases. This enzyme is distinguished from other members of the pepsin family by two features that are characteristic of lysosomal hydrolases. First, mature Cathepsin D is found predominantly in a two-chain form due to a posttranslational cleavage event. Second, it contains phosphorylated, N-linked oligosaccharides that target the enzyme to lysosomes via mannose-6-phosphate receptors. Cathepsin D preferentially attacks peptide bonds flanked by bulky hydrophobic amino acids and its pH optimum is between pH 2.8 and 4.0. Two active site aspartic acid residues are essential for the catalytic activity of aspartic proteinases. Like other aspartic proteinases, Cathepsin D is a bilobed molecule; the two evolutionary related lobes are mostly made up of beta-sheets and flank a deep active site cleft. Each of the two related lobes contributes one active site aspartic acid residue and contains a single carbohydrate group. Cathepsin D is an essential enzyme. Mice deficient for proteinase cathepsin D, generated by gene targeting, develop normally during the first 2 weeks, stop thriving in the third week and die in a state of anorexia in the fourth week. The mice develop atrophy of ileal mucosa followed by other degradation of intestinal organs. In these knockout mice, lysosomal proteolysis was normal. These results suggest that vital functions of cathepsin D are exerted by limited proteolysis of proteins regulating cell growth and/or tissue homeostasis, while its contribution to bulk proteolysis in lysosomes appears to be non-critical. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133157 [Multi-domain] Cd Length: 325 Bit Score: 57.49 E-value: 1.58e-09
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| gastricsin | cd05477 | Gastricsins, asparate proteases produced in gastric mucosa; Gastricsin is also called ... |
1-182 | 2.44e-09 | ||||
Gastricsins, asparate proteases produced in gastric mucosa; Gastricsin is also called pepsinogen C. Gastricsins are produced in gastric mucosa of mammals. It is synthesized by the chief cells in the stomach as an inactive zymogen. It is self-converted to a mature enzyme under acidic conditions. Human gastricsin is distributed throughout all parts of the stomach. Gastricsin is synthesized as an inactive progastricsin that has an approximately 40 residue prosequence. It is self-converting to a mature enzyme being triggered by a drop in pH from neutrality to acidic conditions. Like other aspartic proteases, gastricsin are characterized by two catalytic aspartic residues at the active site, and display optimal activity at acidic pH. Mature enzyme has a pseudo-2-fold symmetry that passes through the active site between the catalytic aspartate residues. Structurally, aspartic proteases are bilobal enzymes, each lobe contributing a catalytic aspartate residue, with an extended active site cleft localized between the two lobes of the molecule. One lobe may be evolved from the other through ancient gene-duplication event. Although the three-dimensional structures of the two lobes are very similar, the amino acid sequences are more divergent, except for the conserved catalytic site motif. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133144 [Multi-domain] Cd Length: 318 Bit Score: 56.82 E-value: 2.44e-09
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| pepsin_A | cd05478 | Pepsin A, aspartic protease produced in gastric mucosa of mammals; Pepsin, a well-known ... |
1-182 | 7.21e-09 | ||||
Pepsin A, aspartic protease produced in gastric mucosa of mammals; Pepsin, a well-known aspartic protease, is produced by the human gastric mucosa in seven different zymogen isoforms, subdivided into two types: pepsinogen A and pepsinogen C. The prosequence of the zymogens are self cleaved under acidic pH. The mature enzymes are called pepsin A and pepsin C, correspondingly. The well researched porcine pepsin is also in this pepsin A family. Pepsins play an integral role in the digestion process of vertebrates. Pepsins are bilobal enzymes, each lobe contributing a catalytic Asp residue, with an extended active site cleft localized between the two lobes of the molecule. One lobe may be evolved from the other through ancient gene-duplication event. More recently evolved enzymes have similar three-dimensional structures, however their amino acid sequences are more divergent except for the conserved catalytic site motif. Pepsins specifically cleave bonds in peptides which have at least six residues in length with hydrophobic residues in both the P1 and P1' positions. The active site is located at the groove formed by the two lobes, with an extended loop projecting over the cleft to form an 11-residue flap, which encloses substrates and inhibitors in the active site. Specificity is determined by nearest-neighbor hydrophobic residues surrounding the catalytic aspartates, and by three residues in the flap. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133145 [Multi-domain] Cd Length: 317 Bit Score: 55.53 E-value: 7.21e-09
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| Cathespin_E | cd05486 | Cathepsin E, non-lysosomal aspartic protease; Cathepsin E is an intracellular, non-lysosomal ... |
1-182 | 1.39e-07 | ||||
Cathepsin E, non-lysosomal aspartic protease; Cathepsin E is an intracellular, non-lysosomal aspartic protease expressed in a variety of cells and tissues. The protease has proposed physiological roles in antigen presentation by the MHC class II system, in the biogenesis of the vasoconstrictor peptide endothelin, and in neurodegeneration associated with brain ischemia and aging. Cathepsin E is the only A1 aspartic protease that exists as a homodimer with a disulfide bridge linking the two monomers. Like many other aspartic proteases, it is synthesized as a zymogen which is catalytically inactive towards its natural substrates at neutral pH and which auto-activates in an acidic environment. The overall structure follows the general fold of aspartic proteases of the A1 family, it is composed of two structurally similar beta barrel lobes, each lobe contributing an aspartic acid residue to form a catalytic dyad that acts to cleave the substrate peptide bond. The catalytic Asp residues are contained in an Asp-Thr-Gly-Ser/thr motif in both N- and C-terminal lobes of the enzyme. The aspartic acid residues act together to allow a water molecule to attack the peptide bond. One aspartic acid residue (in its deprotonated form) activates the attacking water molecule, whereas the other aspartic acid residue (in its protonated form) polarizes the peptide carbonyl, increasing its susceptibility to attack. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133153 [Multi-domain] Cd Length: 316 Bit Score: 51.42 E-value: 1.39e-07
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| renin_like | cd05487 | Renin stimulates production of angiotensin and thus affects blood pressure; Renin, also known ... |
1-184 | 1.36e-06 | ||||
Renin stimulates production of angiotensin and thus affects blood pressure; Renin, also known as angiotensinogenase, is a circulating enzyme that participates in the renin-angiotensin system that mediates extracellular volume, arterial vasoconstriction, and consequently mean arterial blood pressure. The enzyme is secreted by the kidneys from specialized juxtaglomerular cells in response to decreases in glomerular filtration rate (a consequence of low blood volume), diminished filtered sodium chloride and sympathetic nervous system innervation. The enzyme circulates in the blood stream and hydrolyzes angiotensinogen secreted from the liver into the peptide angiotensin I. Angiotensin I is further cleaved in the lungs by endothelial bound angiotensin converting enzyme (ACE) into angiotensin II, the final active peptide. Renin is a member of the aspartic protease family. Structurally, aspartic proteases are bilobal enzymes, each lobe contributing a catalytic Aspartate residue, with an extended active site cleft localized between the two lobes of the molecule. The N- and C-terminal domains, although structurally related by a 2-fold axis, have only limited sequence homology except the vicinity of the active site. This suggests that the enzymes evolved by an ancient duplication event. The active site is located at the groove formed by the two lobes, with an extended loop projecting over the cleft to form an 11-residue flap, which encloses substrates and inhibitors in the active site. Specificity is determined by nearest-neighbor hydrophobic residues surrounding the catalytic aspartates, and by three residues in the flap. The enzymes are mostly secreted from cells as inactive proenzymes that activate autocatalytically at acidic pH. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133154 [Multi-domain] Cd Length: 326 Bit Score: 48.62 E-value: 1.36e-06
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| Proteinase_A_fungi | cd05488 | Fungal Proteinase A , aspartic proteinase superfamily; Fungal Proteinase A, a proteolytic ... |
2-182 | 2.42e-06 | ||||
Fungal Proteinase A , aspartic proteinase superfamily; Fungal Proteinase A, a proteolytic enzyme distributed among a variety of organisms, is a member of the aspartic proteinase superfamily. In Saccharomyces cerevisiae, targeted to the vacuole as a zymogen, activation of proteinases A at acidic pH can occur by two different pathways: a one-step process to release mature proteinase A, involving the intervention of proteinase B, or a step-wise pathway via the auto-activation product known as pseudo-proteinase A. Once active, S. cerevisiae proteinase A is essential to the activities of other yeast vacuolar hydrolases, including proteinase B and carboxypeptidase Y. The mature enzyme is bilobal, with each lobe providing one of the two catalytically essential aspartic acid residues in the active site. The crystal structure of free proteinase A shows that flap loop is atypically pointing directly into the S(1) pocket of the enzyme. Proteinase A preferentially hydrolyzes hydrophobic residues such as Phe, Leu or Glu at the P1 position and Phe, Ile, Leu or Ala at P1'. Moreover, the enzyme is inhibited by IA3, a natural and highly specific inhibitor produced by S. cerevisiae. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133155 [Multi-domain] Cd Length: 320 Bit Score: 47.82 E-value: 2.42e-06
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| TAXi_C | pfam14541 | Xylanase inhibitor C-terminal; The N- and C-termini of the members of this family are jointly ... |
26-182 | 3.24e-06 | ||||
Xylanase inhibitor C-terminal; The N- and C-termini of the members of this family are jointly necessary for creating the catalytic pocket necessary for cleaving xylasnase. Phytopathogens produce xylanase that destroys plant cells, so its destruction through proteolysis is vital for plant-survival. Pssm-ID: 434029 Cd Length: 160 Bit Score: 46.11 E-value: 3.24e-06
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| Aspergillopepsin_like | cd06097 | Aspergillopepsin_like, aspartic proteases of fungal origin; The members of this family are ... |
4-182 | 5.58e-05 | ||||
Aspergillopepsin_like, aspartic proteases of fungal origin; The members of this family are aspartic proteases of fungal origin, including aspergillopepsin, rhizopuspepsin, endothiapepsin, and rodosporapepsin. The various fungal species in this family may be the most economically important genus of fungi. They may serve as virulence factors or as industrial aids. For example, Aspergillopepsin from A. fumigatus is involved in invasive aspergillosis owing to its elastolytic activity and Aspergillopepsins from the mold A. saitoi are used in fermentation industry. Aspartic proteinases are a group of proteolytic enzymes in which the scissile peptide bond is attacked by a nucleophilic water molecule activated by two aspartic residues in a DT(S)G motif at the active site. They have a similar fold composed of two beta-barrel domains. Between the N-terminal and C-terminal domains, each of which contributes one catalytic aspartic residue, there is an extended active-site cleft capable of interacting with multiple residues of a substrate. Although members of the aspartic protease family of enzymes have very similar three-dimensional structures and catalytic mechanisms, each has unique substrate specificity. The members of this family has an optimal acidic pH (5.5) and cleaves protein substrates with similar specificity to that of porcine pepsin A, preferring hydrophobic residues at P1 and P1' in the cleave site. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133161 [Multi-domain] Cd Length: 278 Bit Score: 43.44 E-value: 5.58e-05
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| xylanase_inhibitor_I_like | cd05489 | TAXI-I inhibits degradation of xylan in the cell wall; Xylanase inhibitor-I (TAXI-I) is a ... |
66-182 | 6.75e-04 | ||||
TAXI-I inhibits degradation of xylan in the cell wall; Xylanase inhibitor-I (TAXI-I) is a member of potent TAXI-type inhibitors of fungal and bacterial family 11 xylanases. Plants developed a diverse battery of defense mechanisms in response to continual challenges by a broad spectrum of pathogenic microorganisms. Their defense arsenal includes inhibitors of cell wall-degrading enzymes, which hinder a possible invasion and colonization by antagonists. Xylanases of fungal and bacterial pathogens are the key enzymes in the degradation of xylan in the cell wall. Plants secrete proteins that inhibit these degradation glycosidases, including xylanase. Surprisingly, TAXI-I displays structural homology with the pepsin-like family of aspartic proteases but is proteolytically nonfunctional, because one or more residues of the essential catalytic triad are absent. The structure of the TAXI-inhibitor, Aspergillus niger xylanase I complex, illustrates the ability of tight binding and inhibition with subnanomolar affinity and indicates the importance of the C-terminal end for the differences in xylanase specificity among different TAXI-type inhibitors. This family also contains pepsin-like aspartic proteinases homologous to TAXI-I. Unlike TAXI-I, they have active site aspartates and are functionally active. This family of aspartate proteases is classified by MEROPS as the peptidase family A1 (pepsin A, clan AA). Pssm-ID: 133156 [Multi-domain] Cd Length: 362 Bit Score: 40.41 E-value: 6.75e-04
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| pepsin_A_like_plant | cd05476 | Chroloplast Nucleoids DNA-binding Protease and Nucellin, pepsin-like aspartic proteases from ... |
1-186 | 1.01e-03 | ||||
Chroloplast Nucleoids DNA-binding Protease and Nucellin, pepsin-like aspartic proteases from plants; This family contains pepsin like aspartic proteases from plants including Chloroplast Nucleoids DNA-binding Protease and Nucellin. Chloroplast Nucleoids DNA-binding Protease catalyzes the degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in senescent leaves of tobacco and Nucellins are important regulators of nucellar cell's progressive degradation after ovule fertilization. Structurally, aspartic proteases are bilobal enzymes, each lobe contributing a catalytic Asp residue, with an extended active site cleft localized between the two lobes of the molecule. The N- and C-terminal domains, although structurally related by a 2-fold axis, have only limited sequence homology except the vicinity of the active site. This suggests that the enzymes evolved by an ancient duplication event. The enzymes specifically cleave bonds in peptides which have at least six residues in length with hydrophobic residues in both the P1 and P1' positions. The active site is located at the groove formed by the two lobes, with an extended loop projecting over the cleft to form an 11-residue flap, which encloses substrates and inhibitors in the active site. Specificity is determined by nearest-neighbor hydrophobic residues surrounding the catalytic aspartates, and by three residues in the flap. The enzymes are mostly secreted from cells as inactive proenzymes that activate autocatalytically at acidic pH. Pssm-ID: 133143 [Multi-domain] Cd Length: 265 Bit Score: 39.55 E-value: 1.01e-03
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