Effect of Metabolic Inhibitors on Production of CO 2 and H 2 S by Endamoeba histolytica ∗

Summary

The in vitro effects of several groups of compounds were tested on the rate of CO₂ and H₂S evolution, catalyzed by enzyme systems of E. histolytica. Since the mechanism of the enzymatic reduction of S to H₂S, a reaction which is coupled with the anaerobic oxidation of sugars in this proto-zoon, has been previously elucidated, it was possible to classify inhibitors on the basis of their primary point of attack. Certain anti-biotics were found to interfere with the S reducing enzyme system, while compounds which form metal ion complexes inhibit both C0₂ and H₂S evolution to an equal extent. Arsenate and methylene blue on the other hand inhibit primarily C0₂ evolution (the decarboxylation of pyruvate). Certain heterocyclic N containing compounds (e.g., 2, 3-diaminophenazine), which can trap HS° and also form complexes with metal ions were found to be the most potent inhibitors of enzyme systems of E. histolytica. The metabolic reactions which were investigated are specific for this protozoon, therefore inhibitor studies on these enzyme systems are considered to be the biochemical basis of chemotherapy of amebiasis.