Studies on the Metabolism of Locust Fat Body

Abstract

1. The incorporation of glycine-¹⁴C (G), leucine-¹⁴C (G), sodium acetate-2-¹⁴C and glucose-¹⁴C (G) into Schistocerca fat body was studied under in vitro conditions, and the distribution of radioactivity in the various fat body fractions and the labelling of compounds within the fractions is described. 2. The overall picture was of high incorporation into fat and protein and of very low incorporation into glycogen. 3. Incubation with glycine-¹⁴C led to radioactivity appearing in the glycine and serine of the protein and of the amino acid pool. Incubation with sodium acetate-2-¹⁴C led to radioactivity appearing in glutamate, proline, aspartate and alanine, showing that the intermediates of the tricarboxylic acid cycle provide the carbon skeletons of certain amino acids. Glucose-¹⁴C was largely converted to trehalose. 4. Succinic dehydrogenase and the condensing enzyme system were shown to be present in fat body, contrary to previous reports. The succinic oxidase system was highly labile on homogenizing the tissue. 5. Fat body, unlike flight muscle, used glycine-¹⁴C and leucine-¹⁴C as respiratory substrates, and it is suggested that fat body acts like the vertebrate liver by transdeaminating amino acids and making them available for further metabolism by other tissues.