Cobyrinate a,c-diamide synthase ( EC [1]), cobyrinic acid a,c-diamide synthetase, CbiA (gene)) is an enzyme which catalyses the chemical reaction ^[1]

2 ATP + cobyrinate + 2 L- glutamine + 2 H₂O ${\displaystyle \rightleftharpoons }$ 2 ADP + 2 phosphate + cobyrinate a,c-diamide + 2 L-glutamate (overall reaction)

(1a) ATP + cobyrinate + L-glutamine + H₂O ${\displaystyle \rightleftharpoons }$ ADP + phosphate + cobyrinate c-monamide + L-glutamate

(1b) ATP + cobyrinate c-monamide + L-glutamine + H₂O ${\displaystyle \rightleftharpoons }$ ADP + phosphate + cobyrinate a,c-diamide + L-glutamate

This enzyme is a glutamine amidotransferase, part of the biosynthetic pathway to cobalamin (vitamin B₁₂) in anaerobic bacteria such as Salmonella typhimurium and Bacillus megaterium.

• Cobalamin biosynthesis

• Cobyrinate+a,c-diamide+synthase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)