QUANTITATIVE APPRAISALS OF POSSIBLE CATALYTIC INTERMEDIATES IN SUCCINYL COENZYME A SYNTHETASE REACTION

Previous data have suggested participation of an enzyme-bound form of coenzyme A in the succinyl coenzyme A synthetase reaction. The proposed mechanism requires participation of an oxygen atom from the enzyme or the coenzyme A. Quantitative 18O studies demonstrate a lack of participation of enzyme or of coenzyme A oxygens and a retention of substrate-18O during catalysis of the succinate ⇄ succinyl coenzyme A, phosphate ⇄ phosphoryl enzyme and phosphate ⇄ adenosine triphosphate exchanges. These results together with a lack of detection of covalently bound coenzyme A and other findings provide compelling evidence against participation of an enzyme-bound coenzyme A form in the catalysis. © 1969, American Chemical Society. All rights reserved.