IMPDH/GMPR family
impdh/gmpr family
IMP dehydrogenase (IMPDH) and GMP reductase (GMPR) belong to the same family of (beta/alpha)8 TIM-barrel enzymes. They bind the same ligands with similar affinities and share a common set of catalytic residues. Both enzymes catalyze a hydride transfer reaction involving a nicotinamide cofactor hydride, and both reactions proceed via the same covalent intermediate. In the case of IMPDH, this intermediate reacts with water while in GMPR it reacts with ammonia. In both cases, the two chemical transformations are separated by a conformational change. In IMPDH, the conformational change involves a mobile protein flap while in GMPR the cofactor moves.