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M42 Peptidases, also known as glutamyl aminopeptidase family Peptidase M42 family proteins, also known as glutamyl aminopeptidases (GAP), are co-catalytic metallopeptidases, found in archaea and bacteria. They typically bind two zinc or cobalt atoms and include cellulase and endo-1,4-beta-glucanase (endoglucanase). Some of the enzymes exhibit typical aminopeptidase specificity, whereas others are also capable of N-terminal deblocking activity, i.e. hydrolyzing acylated N-terminal residues. GAP removes glutamyl residues from the N-terminus of peptide substrates, but is also effective against aspartyl and, to a lesser extent, seryl residues. Lactococcus lactis glutamyl aminopeptidase (PepA; aminopeptidase A) has high thermal stability and aids growth of the organism in milk. Pyrococcus horikoshii contain a thermostable de-blocking aminopeptidase member of this family, used commercially for N-terminal protein sequencing.
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