Cobyrinate a,c diamide synthase

Cobyrinate a,c-diamide synthase (EC 6.3.5.11, cobyrinic acid a,c-diamide synthetase, CbiA (gene)) is an enzyme. This enzyme catalyses the following chemical reaction

2 ATP + cobyrinate + 2 L-glutamine + 2 H₂O ⇌ 2 ADP + 2 phosphate + cobyrinate a,c-diamide + 2 L-glutamate (overall reaction)(1a) ATP + cobyrinate + L-glutamine + H₂O ⇌ ADP + phosphate + cobyrinate c-monamide + L-glutamate(1b) ATP + cobyrinate c-monamide + L-glutamine + H₂O ⇌ ADP + phosphate + cobyrinate a,c-diamide + L-glutamate

This enzyme is the first glutamine amidotransferase that participates in the anaerobic biosynthetic pathway of adenosylcobalamin.