Acylation of steryl glucosides by phospholipids. Solubilization and properties of the acyl transferase.

Particulate enzyme preparations of cotton fibers catalyze the acylation of exogenous steryl glucoside to form acylated steryl glucoside. The acyl transferase involved in this reaction was solubilized by treatment of the membrane fractions with Triton X-100 and was partially purified by chromatography on DEAE-cellulose and gel filtration. This solubilized enzyme had an absolute requirement for Triton X-100 and phospholipid in order to catalyze the acylation of the steryl glucoside. The best phospholipid substrate was phosphatidylethanolamine but egg and soybean phosphatidylcholine were also active. The phospholipid was shown to function as an acyl donor by demonstrating that ¹⁴C]fatty acid from ¹⁴C-labeled phospholipid could be transferred to steryl-³H]glucoside to form ¹⁴C,³H]acylated steryl glucoside. Saponification of this compound yielded ¹⁴C]fatty acid and steryl-⁷H]glucoside.