Reaction: Hydrolysis of proteins, with a strong preference for Phe or Tyr at position P1 and one of the smaller amino-acids at P1' in the sequence - P3 - P2 - P1 ┼P1'- P2'- P3'-. Cleaves the Tyr26-Thr27 bond in the B chain of oxidized insulin, which is not cleaved by pepsin.
Other name(s): scytalidopepsin-B; SCP-B; SGP; scytalidocarboxylpeptidase-B
Comments: The enzyme, isolated from the fungus Scytalidium lignicola and found in several other fungi, has a low pH optimum, being most active at pH 2 with casein as substrate. It differs from the pepsins (EC 3.4.23.1 and EC 3.4.23.2) in being insensitive to inhibition by pepstatin. It also differs from mammalian pepsins in showing a preference for a positively charged residue (Lys or Arg) at the P3 position. In addition to the catalytic Glu residue, a Gln residue appears to play an important role in the hydrolytic mechanism. A member of peptidase family G01, the "eqolisin" family of glutamic peptidases (G01.0001).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Kataoka, Y., Takada, K., Oyama, H., Tsunemi, M., James, M.N. and Oda, K. Catalytic residues and substrate specificity of scytalidoglutamic peptidase, the first member of the eqolisin in family (G1) of peptidases. FEBS Lett. 579 (2005) 2991-2994. [PMID: 15907842]
2. Fujinaga, M., Cherney, M.M., Oyama, H., Oda, K. and James, M.N. The molecular structure and catalytic mechanism of a novel carboxyl peptidase from Scytalidium lignicolum. Proc. Natl. Acad. Sci. USA 101 (2004) 3364-3369. [PMID: 14993599]
3. Pillai, B., Cherney, M.M., Hiraga, K., Takada, K., Oda, K. and James, M.N. Crystal structure of scytalidoglutamic peptidase with its first potent inhibitor provides insights into substrate specificity and catalysis. J. Mol. Biol. 365 (2007) 343-361. [PMID: 17069854]
4. Kondo, M.Y., Okamoto, D.N., Santos, J.A., Juliano, M.A., Oda, K., Pillai, B., James, M.N., Juliano, L. and Gouvea, I.E. Studies on the catalytic mechanism of a glutamic peptidase. J. Biol. Chem. 285 (2010) 21437-21445. [PMID: 20442413]