Metabolism Studies by Radiorespirometry

Abstract

Many of the recent advances in the area of carbohydrate catabolism can be credited to the use of radiotracer methods. Although some tritium-labeled compounds have been used for these studies, the majority of research efforts in this regard involved the use of C¹⁴ specifically labeled carbohydrates or allied compounds. The catabolic mechanism for the utilization of a given carbohydrate is commonly elucidated by one or both of two basic approaches [1]. The first is the conversion of specifically labeled carbohydrate into catabolic products in the absence or presence of inhibitors. Isotopic distribution patterns and relative specific activity [2, 3] of a key product or an intermediate often provide important information on the nature and participation of an individual pathway. The discovery of the Entner-Doudoroff (ED) pathway [4] (Fig. 1) is the result of experiments of this type. The second approach is the examination of the respiratory C¹⁴O₂ samples derived from specifically labeled carbon atoms of a given carbohydrate with respect to either the specific activities or yields. Experiments of this type are easy to carry out and provide information on the occurrence and participation of a known pathway in a given biological system.

Presented at the Fifth Symposium on Advances in Tracer Methodology, 1961.