A potent specific inhibitor of 6-phosphogluconate dehydrogenase ofCryptococcus neoformans and of certain other fungal enzymes

A particular lot of the zwitterionic buffer, 2(N-morpholino) ethane sulfonic acid (MES), contained a contaminant that inhibited a number of fungal NADP-dependent dehydrogenases. Enzymes that were particularly sensitive include 6-phosphogluconate dehydrogenases fromCryptococcus neoformans andSchizophyllum commune and glucose-6-phosphate dehydrogenase fromSchizophyllum commune. A number of NADP-dependent dehydrogenases of animal origin were tested and all were completely insensitive to inhibition except for rat liver 6-phosphogluconate dehydrogenase, which was 10-fold less sensitive than theCryptococcal enzyme. The pattern of inhibition in all cases was linear competitive versus NADP. The inhibitor has been purified and identified as an ethylenesulfonic acid oligomer. This inhibitor holds promise as a model compound for the development of a specific antifungal agent.