ACID-SOLUBLE PHOSPHORUS COMPOUNDS AND FREE SUGARS IN FISH MUSCLE AND THEIR ORIGIN

Abstract

An ion-exchange system capable of separating the principal sugar phosphates and nucleotides in fish muscles was developed and used to study the distribution of these in muscles of freshly killed fish, and in certain of these muscles after several days at 0 °C. The results indicate that there are extreme quantitative variations in these compounds. Intravenous introduction of C14-labelled glucose or G6P* into salmonoid fish results in rapid labelling of glycolytic intermediates such as F6P, FDP, and lactate in both muscle and liver. Evidence was obtained, using C14fish muscle glycogen, which indicates that this substance is degraded to maltose and glucose post mortem both by an amylase and by the Embden–Meyerhof system, and that very little glucose arises by hydrolysis of G6P. When introduced into fish muscle post mortem, C14ATP yielded radioactive IMP and ribose, G6P and glucose being unlabelled. Radioactive R5P (or ribose) was never found in muscle of fish injected with C14-labelled glucose or G6P, indicating that these are not formed via the hexosemonophosphate shunt system. R5P was not found in muscle of living fish and only in comparatively small amounts post mortem. Evidence is presented which shows that F1P does not occur in appreciable amounts in fish muscles, and that the evidence so far presented in support of the occurrence of R1P is unsatisfactory.