Family G1


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family G1

Family type peptidaseG01.001 - scytalidoglutamic peptidase (Scytalidium lignicolum), MEROPS Accession MER0001320 (peptidase unit: 58-260)
Content of familyPeptidase family G1 contains endopeptidases from fungi.
History Identifier created: MEROPS 6.6 (27 March 2004)
The peptidases in family G1 form a subset of what were formerly termed "pepstatin-insensitive carboxyl proteinases". After its discovery in about 1970, the pentapeptide pepstatin soon came to be thought of as a very general inhibitor of the endopeptidases that are active at acidic pH. But by 1985, several acid-acting endopeptidases from bacteria and fungi had been found to be resistant to pepstatin. The unusual active sites of the "pepstatin-insensitive carboxyl proteinases" proved difficult to characterise, but it is now been established that the enzymes from bacteria are acid-acting serine peptidases in family S53 (clan SB), whereas the fungal enzymes are in family G1 (formerly A4). The importance of glutamate ("E") and glutamine ("Q") residues in the active sites of the family G1 enzymes led to the proposal to call family G1 the "eqolisin family" (Fujinaga et al., 2004).
Catalytic typeGlutamic
Active site residuesQ107 E190 
Active siteThe tertiary structure of scytalidoglutamic peptidase (G01.001) with a bound tripeptide product has been interpreted as showing that Glu136 is the primary catalytic residue (Fujinaga et al., 2004). The most likely mechanism is suggested to be nucleophilic attack by a water molecule activated by the Glu136 side chain on the si-face of the scissile peptide bond carbon atom to form the tetrahedral intermediate. Electrophilic assistance, and oxyanion stabilisation, are provided by the side-chain amide of Gln53.
Activities and specificitiesBoth scytalidoglutamic peptidase (G01.001) and aspergilloglutamic peptidase (G01.002) cleave (amongst others) the Tyr26Thr27 bond in the B chain of oxidized insulin; a bond not cleaved by other acid-acting endopeptidases. Scytalidoglutamic peptidase is most active on casein at pH 2.
InhibitorsScytalidoglutamic peptidase is inhibited by 1,2-epoxy-3-(p-nitrophenoxy)propane (EPNP) (Oda, 2004), a compound that also inhibits pepsin (A01.001).
Molecular structureThe molecule of scytalidoglutamic peptidase is a beta-sandwich in which each sheet has seven anti-parallel strands (Fujinaga et al., 2004).
Distribution of family Bacteria details  
Archaea details  
Protozoa -  
Fungi details  
Plants -  
Animals -  
Viruses -  
Biological functionsThe peptidases may well contribute to the nutrition of the fungi in which they occur.
Statistics for family G1Sequences:268
Identifiers with PDB entries:2
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
scytalidoglutamic peptidaseG01.001Yes
aspergilloglutamic peptidaseG01.002Yes
peptidase EapBG01.003-
peptidase EapCG01.004-
PMAP-1 peptidase (Penicillium marneffei)G01.005-
PepG1 peptidase (Alicyclobacillus sp.)G01.006-
family G1 non-peptidase homologuesnon-peptidase homologue-
family G1 unassigned peptidasesunassigned-