IUBMB Enzyme Nomenclature


Accepted name: spermosin

Reaction: Hydrolyses arginyl bonds, preferably with Pro in the P2 position

Comments: The enzyme from the ascidian (Prochordate) Halocynthia roretzi is localised in the sperm head, and released during sperm activation. A proline-rich region is involved in binding to the vitelline coat of the egg. Belongs in peptidase family S1 (trypsin family).

Links to other databases: BRENDA, EXPASY, KEGG, MEROPS, Metacyc, PDB, CAS registry number: 89925-67-7


1. Sawada, H., Yokosawa, H. and Ishii, S. Purification and characterization of two types of trypsin-like enzymes from sperm of the ascidian (Prochordata) Halocynthia roretzi. Evidence for the presence of spermosin, a novel acrosin-like enzyme. J. Biol. Chem. 259 (1984) 2900-2904. [PMID: 6365918]

2. Sawada, H., Yokosawa, H., Someno, T., Saino, T. and Ishii, S. Evidence for the participation of two sperm proteases, spermosin and acrosin, in fertilization of the ascidian, Halocynthia roretzi: inhibitory effects of leupeptin analogs on enzyme activities and fertilization. Dev. Biol. 105 (1984) 246-249. [PMID: 6381175]

3. Sawada, H., Iwasaki, K., Kihara-Negishi, F., Ariga, H. and Yokosawa, H. Localization, expression, and the role in fertilization of spermosin, an ascidian sperm trypsin-like protease. Biochem. Biophys. Res. Commun. 222 (1996) 499-504. [PMID: 8670234]

4. Sawada, H. and Someno, T. Substrate specificity of ascidian sperm trypsin-like proteases, spermosin and acrosin. Mol. Reprod. Dev. 45 (1996) 240-243. [PMID: 8914083]

[EC created 2001]

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