Inhibition of glucose assimilation and transport by n-decane and other n-alkanes in Candida 107.

Abstract

SUMMARY: Candida 107 constitutively oxidizes n-nonane and longer alkanes. Decane and longer alkanes have little effect on endogenous respiration (measured as 14CO2 expiration from yeast grown on [U-14C]glucose). Alkane-grown yeast assimilated [1-14C]decane more rapidly than glucose-grown yeast though without a lag in both cases. Glucose did not inhibit these incorporations. [U-14C]Glucose was assimilated without a lag into glucose-grown yeast and, at a quarter of this rate, into alkane-grown yeast: if the latter yeast was pre-incubated with glucose for 60 min, it took up [U-14C]glucose at the higher rate. n-Decane (0.5 to 1.0 mg/mg yeast dry wt) severely and rapidly inhibited glucose assimilation. Longer chain alkanes were progressively less effective. All alkanes were more inhibitory with alkane-grown yeast. The rate of glucose assimilation was inversely proportional to the concentration of decane and directly proportional to the yeast concentration. Transport of glucose, as distinct from its assimilation, was also inhibited by decane. Uptake of fucose, a non-metabolizable deoxyhexose, was similarly affected. Passive transport of glucose did not occur. Alkanes did not prevent glucose access to the yeast surface as pristane, a non-metabolizable paraffin, had no effect on glucose assimilation in Candida 107 and dodecane was not inhibitory against carbohydrate transport in Saccharomyces carlsbergensis. Alkanes probably inhibit by causing accumulation of fatty acids or acyl CoA esters which may, either through feedback inhibitions or by further metabolism, cause build-up of ATP, acetyl CoA, and glucose 6-phosphate, thus leading to cessation of glucose transport and metabolism.