Aerobic metabolism of the muscle of Locusta migratoria

Abstract

O2 uptake of suspensions of L. migvatoria muscle was increased by fructose-6-phosphate, hexose, diphosphate, phosphoglyceric acid, l-malate, succinate, oxalacetate, alpha-oxoglutarate, fumarate, cis-aconitate, pyruvate. It was inhibited by malonate and arsenite, with the latter allowing the accumulation of pyruvate. Citrate was synthesized from oxal-acetate and pyruvate and alpha-oxoglutarate converted to succinate. With sarcosomes prepared from muscle, diphosphopyri-dine nucleotide (DPN) and the supernatant fluid from which they had been isolated, yeast juice and ethylenediaminetetraacetic acid caused a large increase in respiration, but not adonosine-triphosphate (ATP), adenosine diphosphate (ADP), flavin-adenine-nucleotide (FAD), glutathione (GSH), thiamine pyrophosphate (TPP) or CoA or histidine. Citric acid was oxidized by sarco-somes only with added triphosphopyridine nucleotide (TPN), or ATP + DPN. Endogenous respiration and oxidation of citric acid cycle intermediates was accompanied by the esterification of inorganic phosphate but added hexokinase had little effect due to the large amounts of hexose and hexokinase present. Fluoride inhibited respiration of muscle suspensions in the presence and absence of citric acid cycle intermediates. P/O ratios were of the same order as for mammalian tissue. Oxidative phosphorylation by sarcosomes was also stimulated by supernatant fluid, yeast juice and EDA. The latter suggests that this is due to removal of inhibitory metals.