Cobyrinate a,c-diamide synthase (EC ), cobyrinic acid a,c-diamide synthetase, CbiA (gene)) is an enzyme which catalyses the chemical reaction2 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