Abstract
The exchange of tritium from meso-2,3-ditritiosuccinate and racemic-2-tritiosuccinate to water was studied using soluble and particulate preparations of succinic dehydrogenase from heart muscle. All the tritium exchanges. We conclude from kinetics that the enzyme fails to discriminate strongly among hydrogen atoms at the 2,3-methylene positions. A strongly differential retention of hydrogen, predicted by the work of Gawron and co-workers and attributed to enzyme asymmetry, is not observed. Complete exchange confirms the early observation of
Weinmann et al. (1947). Since the exchange reaction does not show an obligatory requirement for fumaric acid, exchange can occur from the enzyme-succinate complex. The results support the view that exchange proceeds by the exchange of a trans pair of hydrogen atoms.