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M42 Peptidase, endoglucanases Peptidase M42 family, Frv (Frv Operon Protein; Endo-1 4-Beta-Glucanase; Cellulase Protein; Endoglucanase; Endo-1 4-Beta-Glucanase Homolog; Glucanase; EC. 3.2.1.4) subfamily. Frv is a co-catalytic metallopeptidase, found in archaea and bacteria, including Pyrococcus horikoshii tetrahedral shaped phTET1 (DAPPh1; FrvX; PhDAP aminopeptidase; PhTET aminopeptidase; deblocking aminopeptidase), phTET2 (DAPPh2) and phTET3 (DAPPh3), Haloarcula marismortui TET (HmTET) as well as Bacillus subtilis YsdC. All of these exhibit aminopeptidase and deblocking activities. The HmTET is a broad substrate aminopeptidase capable of degrading large peptides. PhTET2, which shares 24% identity with HmTET, is a cobalt-activated peptidase and possibly a deblocking aminopeptidase, assembled as a 12-subunit tetrahedral dodecamer, while PhTET1 can be alternatively assembled as a tetrahedral dodecamer or as an octahedral tetracosameric structure. The active site in such a self-compartmentalized complex is located on the inside such that substrate sizes are limited, indicating function as possible peptide scavengers. PhTET2 cleaves polypeptides by a nonprocessive mechanism, preferring N-terminal hydrophobic or uncharged polar amino acids. Streptococcus pneumoniae PepA (SpPepA) also forms dodecamer with tetrahedral architecture, and exhibits selective substrate specificity to acidic amino acids with the preference to glutamic acid, with the substrate binding S1 pocket containing an Arg allows electrostatic interactions with the N-terminal acidic residue in the substrate. The YsdC gene is conserved in a number of thermophiles, archaea and pathogenic bacterial species; the closest structural homolog is Thermotoga maritima FrwX (34% identity), which is annotated as either a cellulase or an endoglucanase, and is possibly involved in polysaccharide biosynthesis or degradation. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",