Reaction: 6-(L-cystein-S-yl)-6-deoxy-5'-guanylate + H2O = 6-thio-5'-guanylate + pyruvate + ammonium (overall reaction)
(1a) 6-(L-cystein-S-yl)-6-deoxy-5'-guanylate = 6-thio-5'-guanylate + 2-aminoprop-2-enoate
(1b) 2-aminoprop-2-enoate = 2-iminopropanoate (spontaneous)
(1c) 2-iminopropanoate + H2O = pyruvate + ammonium (spontaneous)
Other name(s): ycfC (gene name); 6-(S-L-cysteinyl)-GMP lyase
Systematic name: 6-(L-cystein-S-yl)-6-deoxy-5'-guanylate 6-thio-5'-guanylate-lyase (deaminating; pyruvate-forming)
Comments: A pyridoxal 5'-phosphate protein. The enzyme, characterized from the plant pathogen Erwinia amylovora, is involved in production of 6-thioguanine, a virulence factor involved in the fire blight disease, which infects apples and pears. The enzyme cleaves a carbon-sulfur bond, likely releasing a thiol and an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form pyruvate and ammonia.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Litomska, A., Ishida, K., Dunbar, K.L., Boettger, M., Coyne, S. and Hertweck, C. Enzymatic thioamide formation in a bacterial antimetabolite pathway. Angew. Chem. Int. Ed. Engl. 57 (2018) 11574-11578. [PMID: 29947149]
2. Ishida, K., Litomska, A., Dunbar, K.L. and Hertweck, C. An enzymatic prodrug-like route to thio and selenoamides. Angew. Chem. Int. Ed. Engl. 63 (2024) e202404243. [PMID: 38747847]