Homogenates of early chick embryos and homogenates of early chick embryonic hearts utilized the phosphogluconate pathway of glucose catabolism to a greater extent, relative to the glycolytic-Krebs cycle pathway, than did homogenates of hearts from older chick embryos or adult chicks. An abrupt drop in the relative participation by the phosphogluconate pathway in embryo heart homogenates occurs at about 5 to 7 days of incubation. Heart homogenates from adult chicks catabolize glucose almost entirely by the glycolytic-Krebs cycle pathway, with negligible participation by the phosphogluconate pathway.
1. Oxidative dissimilation has been studied in enzymes from the honey bee. Using mitochondria isolated from the thoraces, complete oxidation of most of the TCA cycle members has been shown. 2. The presence of the acetate-activating enzyme, citrate-condensing enzyme, isocitric dehydrogenase, α-ketoglutarate dehydrogenase, glucose-6-phosphate, and 6-phosphogluconic dehydrogenase has been demonstrated and the cofactor requirements established. 3. The oxidation of isocitric acid has been shown to be either non-specific for the D- or L-isomer, or the presence of a racemase is indicated. 4. The presence of the pentose cycle is indicated in the soluble portion of the thoracic homogenate.