Biochemical Properties of Enzymes Present in Microsomal Fractions of Arabidopsis Leaves Involved in Synthesis of Esters of Free Fatty Acids with Alcohols of Different Chain Lengths.

In the performed studies, microsomal fractions from Arabidopsis plants were used as a source of enzymes that esterify free fatty acids to free alcohols (both fatty alcohols and short-chain alcohols). The existence of two isoforms of tested enzymes is postulated. These putative isoforms, characterized by apparent peak activities at pH 6.0 and pH 7.2, respectively, appeared to differ in their responses to environmental conditions, e.g., in their temperature dependence; in their responses to calcium and magnesium ions' presence in assays; or in retaining activity after membrane solubilization with 4% detergent CHAPS (only the postulated isoforms most active at pH 6.0 kept their activity). Differences were also annotated in the preferences of the apparent enzymatic activities toward different fatty alcohols (although both putative isoforms showed the highest activity toward phytol) and different fatty acids (in reactions with both fatty alcohols and short-chain alcohols). Two apparent enzymatic activities were inhibited by tetrahydrolipstatin, which may suggest their lipase nature. Based on the high activity of the tested enzymes in the membrane of the microsomal fractions, the authors speculate that their physiological function might be associated with maintaining membrane integrity against the harmful effects of excess free fatty acids and/or free fatty alcohols.