Selectivity of Celite-Immobilized Patatin (Lipid Acyl Hydrolase) from Potato (Solanum t uberosum L.) Tubers in Esterification Reactions As Influenced by Water Activity and Glycerol Analogues as Alcohol Acceptors

Lipid acyl hydrolase (LAH; patatin) was purified from potato tubers by ammonium sulfate fractionation followed by anion-exchange and affinity chromatography. The major protein band of 40−43 kDa on SDS−PAGE appeared to be patatin, and it stained positive for lipase activity on native PAGE. Selectivity of a Celite-immobilized potato LAH in esterification reactions with n-acyl fatty acids (FA; C4, C6, C8, C10, C12, C14, C16, and C18) and alcohol acceptors (n-propanol, 2-propanol, 1,3-propanediol, and glycerol; 1,2-propanediol was not sufficiently reactive) was studied in isooctane. Immobilized LAH was highly selective for medium chain FAs (C8/C10) with a secondary optimum for chain lengths of C14/16. Water activity (a w) influenced activity and FA selectivity of the enzyme. Initial rates of ester synthesis were greatest at a w of 0.90 for all alcohol acceptors except for glycerol, where greatest initial rates were observed at a w of 0.19. Immobilized LAH preparations exhibited a bell-shape pH profile with optimum activity at pH 6−7 for ester synthesis, and no effect of pH on FA selectivity was observed. Keywords: Patatin; potato lipid acyl hydrolase; fatty acid selectivity; esterification; microaqueous enzymology