Discussion on the Classification Standard of Synthetases by the International Enzyme Committee from the Classification of Phosphoenolpyruvate Carboxylase

By comparing the reaction catalyzed by phosphoenolpyruvate carboxylase with the one by the ligase or synthetase, it was suggested here that phosphoenolpyruvate carboxylase (EC 4.1.1.31, PEPC) should be classified as the synthetase. And accordingly it was thought here that the existing classification standard of synthetases put forward by the International Enzyme Committee should be supplemented. That is, synthetases should also include the enzyme which catalyzes the non phosphoric acid portion of a high-energy phosphoric acid compound (except (d)NTP) to synthesize one new substance with the other substance, meanwhile the high-energy phosphoric acid compound above is hydrolyzed in the reaction accompanying with the release of energy stored in its high-energy phosphate bond. It was suggested here that the formula of the reaction catalyzed by the enzyme should be X~Pi + Y + H₂O → H₃PO₄ + X-Y.