GLUCOSE CATABOLISM IN THE ERGOT FUNGUS, CLAVICEPS PURPUREA

Abstract

The fungus was grown in submerged, aerated, liquid culture. Cell-free preparations were obtained by sonic disintegration followed by low-speed centrifugation. The enzymes of the Embden-Meyerhof-Krebs cycle route of glucose catabolism were demonstrated by the extent to which several intermediates of this pathway were oxidized, as measured by the reduction of triphenyltetrazolium chloride. It was necessary to use such an artificial electron acceptor, since molecular O would not serve as the acceptor in cell-free extracts. Various individual enzyme reactions of the glycolysis-Krebs cycle route, and the pentose phosphate pathway were studied chemically, chromatographically, and spectrophotometrically. The existence of the following enzymes was demonstrated: hexokinase, phosphohexoisomerase, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoriboisom-erase, phosphoketopentoeprimerase, transketolase, transaldolase, aldolase, and fructose 6-phosphate kinase. The time-course oxidation of various specifically C14-labeled forms of glucose, gluconolactone, and ribose was followed by the technique of radiorespirometry. Growing cells of C. purpurea were calculated to employ the glycolysis-Krebs cycle route for about 90% of its glucose catabolism, with the remaining 10% apparently being dissimilated by the pentose cycle. A similar study with resting cells revealed an increased preference for the former pathway, resulting in a decrease of 50 to 60% in the utilization of the latter route.