Characteristics of changes in fatty acid metabolism by suppression of the activities of peroxisomal .BETA.-oxidation system and glyoxylic acid cycle in Tetrahymena pyriformis.

Abstract

The effects of inhibitors on peroxisomal enzymes were examined in order to clarify the role of peroxisomes in the grouwth of Tetrahymena pyriformis. With the supplementation of chlorpromazine, known as an inhibitor of the peroxisomal β-oxidation system, to the culture medium, the growth of T. pyriformis was suppressed and the activity of the glyoxylate cycle which is linked to β-oxidation, was reduced. Supplementation of itaconic acid to the medium, a competitive inhibitor of isocitrate lyase of the glyoxylic acid cycle, also inhibited the growth. In these cases, no change in the activity of mitochondrial β-oxidation was observed. On the other hand, in an experiment concerning the fatty acid metabolism using [U-14C]palmitic acid conversions to glycogen and proteins were significantly inhibited by these inhibitors. Thus, a decrease in the supply of carbon atoms, which are necessary for energy production and the biosynthesis of materials used in cell construction, was suggested. The acyl-coenzyme A not subjected to β-oxidation might be used for lipid synthesis, resulting in an accumulation of triglyceride and phospholipids.From these results, it was concluded that in Tetrahymena peroxisome is not merely an assistant in the mitochondrial metabolic system, but has an important role in the production of energy essential for cell movement and cell growth, and in the conversion of fatty acids to carbohydrates and proteins.