Effect of thiamin deficiency on wax ester fermentation in Euglena gracilis.

Abstract

In Euglena gracilis, the activity of pyruvate: NADP+ oxidoreductase, a novel pyruvate dehydrogenase, was lowered by a deficiency of thiamin in the cells, showing that the enzyme is dependent on thiamin pyrophosphate. In thiamin-sufficient cells, wax esters were rapidly synthesized from paramylon, the reserve polysaccharide, to generate ATP under anaerobiosis (wax ester fermentation), however, wax esters increased less under anaerobiosis in thiamin-deficient cells, demonstrating that pyruvate: NADP+ oxidoreductase participates in wax ester fermentation. In contrast, the paramylon content of deficient-cells rapidly decreased during the initial 12hr anaerobic incubation. Lactate, ethanol and propanol were produced on anaerobic incubation of deficient cells, but their amounts were significantly small compared with the amount of decomposed paramylon. It is suspected that unknown product(s) are synthesized from paramylon on anaerobic incubation in thiamin-deficient cells. During anaerobic incubation of thiamin-deficient cells the ATP level decreased rapidly and the number of living cells also decreased. These results indicate that the formation of wax esters is important for the generation of ATP in anaerobically incubated Euglena cells for survival and that thiamin is an essential factor in the mechanism.