The Use of C14O2 Yields from Glucose-1- and -6-C14 for the Evaluation of the Pathways of Glucose Metabolism

Katz and Wood (1, 2) examined methods that use differently labeled types of glucose for the evaluation of pathways of glucose metabolism.They indicated that any method must encompass several considerations:(a) the pentose cycle' entails synthesis of fructose 6-phosphate and therefore there may be recycling of the hexose phosphates; (b) in addition to the pentose cycle and Embden-Meyerhof pathways, some of the carbohydrate may be metabolized by nontriose phosphate pathways;' (c) the oxidation of triose phosphate to CO2 usually is incomplete.The relative yield of Cl4 from glucose-l-Cl4 and glucose-6-Cl4 in triose phosphate derivatives such as lactate, fatty acids, or CO% was shown (1, 2) to be a nonlinear function of two or three independent variables with no simple relationship to the separate pathways.However, it was shown that when metabolism by only the pentose cycle and Embden-Meyerhof pathways occurs, the pathways can be evaluated from the ratio of Cl4 in triose-P