Enoyl Coenzyme A Hydratase (Crotonase) ENHANCEMENT OF THE RATE OF HYDRATION OF CROTONYLPANTETHEINE BY COENZYME A AND RELATED COMPOUNDS

Abstract The apparent rate of hydration of crotonylpantetheine is stimulated by coenzyme A, a finding in accord with earlier observations. Other compounds, such as ADP, ATP, and acetyl-CoA act in a similar manner. The action of coenzyme A was interpreted earlier to be the result of the "thioltranscrotonylation" activity of crotonase. It was presumed that crotonase catalyzed the transfer of the crotonyl moiety of crotonylpantetheine to coenzyme A and the resulting crotonyl coenzyme A was rapidly hydrated. Reaction of crotonylpantetheine and crotonase with either coenzyme A or acetyl coenzyme A has been found to give only β-hydroxybutyryl-pantetheine and neither crotonyl- nor β-hydroxybutyryl coenzyme A. These observations indicate that crotonase lacks a thioltranscrotonylation activity. The stimulation of the rate of hydration of crotonylpantetheine by coenzyme A and similar compounds appears to occur because of an increased affinity of the enzyme for crotonylpantetheine in the presence of these compounds. It has also been found that the thiol groups in the enzyme, which were postulated to be involved in its thioltranscrotonylation activity as well as hydrase activity, are not essential for the catalytic action of crotonase.