    2.8.3.18 | succinyl-CoA + acetate = acetyl-CoA + succinate |
the general half-reaction for class I CoA-transferases shows two tetrahedral oxyanion intermediates, which differ by whether CoA becomes attached to the external carbonyl, provided by the acyl-CoA/carboxylate substrate, or the internal carbonyl, provided by the essential active-site glutamate. Following exchange of the carboxylate product, the second half-reaction proceeds in the reverse order of the first half-reaction. In the first half-reaction, the binary enzyme·acyl-CoA complex is converted into a CoA thiolate complex that also contains an acylglutamyl anhydride adduct. Ping-pong kinetic mechanism. Val270 has a dual influence on carboxylate substrate selectivity, as a gate and as a clamp, Arg228 has an important kinetic role in carboxylate substrate binding. The auxiliary site nonselectively binds carboxylates at the threshold of the catalytic pocket, while selectivity is enforced by the conserved gating residue Val270 and the interior of the catalytic pocke |
-, 721675 |
