Connective tissue growth stimulated by carrageenin. 3. The nature and amount of polysaccharide produced in normal and scorbutic guinea pigs and the metabolism of a chondroitin sulphuric acid fraction

Abstract

Such an action of propionate is not supported by the relatively small inhibition of acetylation ob- tained with the soluble preparations. It is, how- ever, not necessarily excluded by this result; two possibilities might be suggested. Inhibition may be caused, not by propionate, but by a metabolite of propionate such as propionyl-coenzyme A, which may occur in much higher concentration at the active enzyme site in the mitochondria than is attained in the soluble system. The relatively slow oxidation of propionate by rat-liver homogenates may result in the accumulation of an intermediate in greater concentration than would occur if the metabolism of propionate proceeded normally. A second possibility is suggested by the work of Aisenberg & Potter ( It is conceivable that a parallel situation occurs in rat liver, i.e. that the cell contains two acetic thiokinases and the one within the mitochondria is more susceptible to inhibition by propionate. The present results could then be explained if, of the two, only the mito- chondrial enzyme were linked with the enzymes of the Krebs cycle. Both of these possibilities should be open to testing. SUMMARY 1. The production of 14CO2 from carboxyllabelled acetate by rat-liver homogenates was almost completely abolished by propionate in only one-tenth of the concentration of the acetate.