Studies on the enzymic oxidation of succinic acid containing deuterium in the methylene groups

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Abstract
Succinic acids were prepared, containing 77 atom % and 42 atom % of D in the methylene groups. Succinic acid containing 77 atom % D in the methylene groups was oxidized by a succinic oxidase prepn. at about 40% of the rate of oxidation of normal succinic acid under the same conditions. Succinic acid containing 42 atom % D in the methylene groups was oxidized at about 70% of the rate of oxidation of normal succinic acid. The activation energy of the reaction involving succinic acid containing 77 atom % D in the methylene groups was found to be 1450 [plus or minus] 450 calories higher than the activation energy of the reaction involving normal succinic acid. The affinity of the succinic oxidase prepn. for normal succinic acid was found to be about 1.45 times its affinity for succinic acid containing 77 atom % D in the methyl groups. The results are discussed, particuarly in relation to the use of D as a tracer in biological expts.