Changes in Fungi with Age II. Respiration and Respiratory Enzymes of \u3ci\u3eRhizoctonia solani \u3c/i\u3eand \u3ci\u3eSclerotium bataticola\u3c/i\u3e

The rate of respiration of Rhizoctonia solani and Sclerotium bataticola decreased with age. This decrease in respiratory rate might be produced by a decrease in the specific activity of one or more enzymes involved in carbohydrate metabolism. Specific activities in cell-free extracts were measured for most of the enzymes in the hexose monophosphate shunt, Embden-Meyerhof-Parnas pathway, tricarboxylic acid cycle, and terminal electron-transport system. In addition, glucose oxidase, isocitritase, and malic enzyme were measured. In R. solani, increases in activity with age occurred for hexokinase, α-glycerolphosphate dehydrogenase, malic dehydrogenase, and cytochrome oxidase. Decreases occurred for phosphohexokinase, aconitase, nicotinamide adenine dinucleotide-specific isocitric dehydrogenase, reduced nicotinamide adenine dinucleotide oxidase, and at least one of the enzymes between 3-phosphoglycerate and pyruvate. In S. bataticola, increases in activity with age were observed for phosphohexokinase, pyruvic dehydrogenase, fumarase, malic dehydrogenase, and malic enzyme, whereas none of the enzymes decreased. The specific activities of the remaining enzymes did not change with age in either fungus