Hypoglycin A: A Specific Inhibitor of Isovaleryl CoA Dehydrogenase

Evidence is presented for the specific in vivo and in vitro inhibition of isovaleryl CoA dehydrogenation by hypoglycin A and its derivative, alpha-ketomethylenecyclopropylpropionic acid. alpha-Methylbutyryl CoA dehydrogenation was also impaired, but the degree of inhibition was much lower. Isobutyryl CoA dehydrogenation was not inhibited. 4-Pentenoic acid inhibited none of these reactions. It is concluded that isovaleryl CoA is dehydrogenated by a specific enzyme, isovaleryl CoA dehydrogenase, contrary to previous assumptions that it is dehydrogenated by green acyl CoA dehydrogenase. The present concept agrees with our previous findings in isovaleric acidemia, a genetic disorder in which a specific defect of isovaleryl CoA dehydrogenase was observed. It was also demonstrated that isovaleric acidemia can be induced in experimental animals by the administration of hypoglycin A. Furthermore, some symptoms of "the vomiting sickness of Jamaica" appear to be due to isovaleric acid accumulation secondary to the ingestion of hypoglycin A.