Sulfhydryl nature of active groups in aconitase

Abstract

1. The inhibition of aconitase by p-chloromercuribenzoic acid has been demostrated. No difference in the extent of inhibition was observed when either isocitric or cis-aconitic acid was used as substrate.

2. It has been shown that the inhibition produced by p-chloroniercuric acid could be reversed by the addition of glutatliíone or Bal and that the reversal was greater when cis aconitic acid was used as substrate.

3. The kinetics of inhibition and reactivation were studied and revealed that reactivation of the cis-aconitici acid System is more extensive than that of the isocitric acid System in the intial 20 minutes of the reaction of inhibitor with the enzyme. As the reaction proceeds, this difference bccomes less marked.

4. O-iodoso-benzoic acid was also found to inhibit aconitase. The extent of this inhibiton was idenical for both substrates.

5. lodoacetate, iodoacetamide, were found to be ineffective as inhibitors of aconitase.

6. It is concluded that aconitase is an enzynie requiring an intanct sulfliydryl groups for its activity.