Metabolism of digestive products in the tsetse fly, Glossina morsitans

Abstract

The metabolism of amino acids during early stages of the hunger cycle in the tsetse fly Glossina morsitans was investigated by the use of 14C-labelled amino acids. Three types of amino acid were distinguished on the basis of utilization pattern. Amino acids of the first type, of which leucine is an example, were rapidly metabolized with the bulk of radioactivity appearing in carbondioxide. The early appearance of substantial radioactivity in proline suggests that their oxidation may in part involve a preliminary conversion to proline. Amino acids of the second type, with serine as an example, were less rapidly metabolized and the bulk of radioactivity appeared in uric acid. The supply of serine and glycine carbon for uric acid synthesis was supplemented by conversion of alanine, and other amino acids contributed to uric acid carbon to the extent that they constituted a source of alanine or of carbondioxide. The metabolism of the third type of amino acid, exemplified by proline and glutamate, was very much slower, apparently due to the sequestration of these substrates in the fat body. Amino acids of all categories were found to provide raw material for the synthesis of triglyceride stores to the extent that they contributed to the pool of acetyl CoA.