Regulation of aerobic fermentation in protozoans. VI Comparative biochemistry of pathogenic and nonpathogenic protozoans.

We have investigated the oxidation of carbohydrate by several protozoan organisms. The oxidation is incomplete and results in a mixture of organic acid and carbon dioxide. The phosphofructokinase and pyruvate kinase, enzymes normally under strict metabolic regulation, are not subject to the normal feedback inhibition or activation mechanisms found in other cells. Moreover, our investigations and those of others support the hypothesis that a primary pathway for glucose metabolism is to phosphoenolpyruvic acid and then to oxalacetic acid with subsequent reduction to succinic acid.