1.7.1.7 IMP + NH3 + NADP+ = GMP + NADPH + H+ catalytic reaction mechanism, overview. GMPR catalyzes two different chemical transformations at the same active site via two different cofactor conformations, analysis by subtesla high resolution field cycling NMR relaxometry 742897 1.7.1.7 IMP + NH3 + NADP+ = GMP + NADPH + H+ first order reaction 394290 1.7.1.7 IMP + NH3 + NADP+ = GMP + NADPH + H+ mechanism: ordered sequential with GMP binding first 394287 1.7.1.7 IMP + NH3 + NADP+ = GMP + NADPH + H+ ordered bi-bi kinetic mechanism, in which GMP binds first to the enzyme followed by NADPH binding, and NADP+ dissociates first followed by IMP release. GMP and IMP binding are thermodynamically favorable processes. Hydride transfer contributes to the rate-limiting step, and protonation and hydride transfer steps take place in the same transition state, lending support to a concerted mechanism. Product release does not contribute to the rate-limiting step of the reaction 725943 1.7.1.7 IMP + NH3 + NADP+ = GMP + NADPH + H+ ordered bi–bi kinetic mechanism, in which GMP binds first to the enzyme followed by NADPH binding, and NADP+ dissociates first followed by IMP release 725943