Possible Involvement of Acetyl Coenzyme A Carboxylase as Well as Fatty Acid Synthetase in the Temperature-Controlled Synthesis of Fatty Acids in Saccharomyces cerevisiae1

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Abstract
Fatty acid synthetase (FAS) preparations from Saccharomyces cerevisiae cells grown at either 35 or 10°C produced the same products at different temperatures and showed quite similar temperature-dependencies in Arrhenius plots, with break points at 25°C. This break point does not appear to reflect a phase transition of phos-pholipids present in the purified FAS preparations but rather is associated with protein conformational changes. S. cerevisiae cells grown at 35°C and then shifted to 10°C produced fatty acids with a shorter average chain length than those fatty acids synthesized at 10°C by cells already adapted to 10°C (hyper response). Acetyl-CoA carboxylase activity was relatively higher in the cells grown at 35°C than in the cells grown at 10°C; moreover, fatty acids with longer average chain lengths were synthesized in vitro at higher malonyl-CoA concentrations, which was consistent with the difference in the average chain lengths of newly synthesized fatty acids in cells grown at 35 and 10°C. However, the activity levels of acetyl-CoA carboxylase and fatty acid synthetase alone did not account for the hyper response phenomena.