The positional and fatty acid selectivity of oat seed lipase in aqueous emulsions

Abstract

The positional and fatty acid selectivities of oat (Avena sativa L.) seed lipase (triacylglycerol hydrolase EC 3.1.1.3) were examined. Pure triacylglycerols were used as substrates. The products of lipolysis were examined by thin‐layer chromatography and gas‐liquid chromatography. Only symmetrical triacylglycerols were used as substrates; thus potential complications arising from stereobias were avoided. Controls were carried out with a lipase specific for primary positions. The lipase from oat seeds catalyzed the hydrolysis of both primary and secondary esters. When the lipase was tested upon mixtures of homoacid triacylglycerols (triacylglycerols composed of the same three fatty acids), the lipase acted most rapidly upon those containing oleate, elaidate, linoleate and linolenate. Strong intermolecular selectivity against homoacid triacylglycerols containing palmitate, petroselinate and stearate was observed. Comparison of assays performed at 26°C with those performed at 45°C showed that selectivity was temperature‐independent. When mixed‐acid triacylglycerols containing both oleate and stearate were treated with lipase, intramolecular selectivity was observed, with oleate hydrolysis predominating. From this work and earlier work, it can be concluded that the selectivity exhibited by the oat seed lipase is similar to that of the lipase fromGeotrichum candidum, except that the oat seed lipase attacks elaidate, a fatty acyl group with atrans double bond, whereas theG. candidum lipase strongly discriminates against elaidate.

Lipase Activity and Lipid Metabolism During Oat Malting

“…Berner and Hammond (1970) showed that oat lipase favored linoleic acid and discriminated against palmitic acid when presented with various natural TG-containing substrates. Piazza et al (1992), using pure TG as substrates, reported that oat lipase favored oleic, linoleic, and linolenic acids and discriminated against palmitic and stearic acids. The trends in changing fatty acid composition of the FFA fraction that we report here are in accord with the reported lipase selectivities.…”

Plant lipases and their applications in oils and fats modification

“…Concerning cereals, the most extensively studied lipase is probably the one from oat. For example, Piazza et al studied its positional and fatty acid selectivity ten years ago using pure homogeneous triacylglycerols [8]. It was observed that this lipase hydrolysing both primary and secondary esters did not exhibit any positional specificity.…”

Lipid-modifying enzymes in oat and faba bean

“…Although detrimental effects of lipase on oat lipids and of LOX on faba bean lipids are well described (Piazza, Bilyk, Brower, & Haas, 1992;Clemente et al, 2000;Lehtinen & Kaukovirta-Norja, 2011), there is very little knowledge on the overall effects of the lipid-modifying enzymes on oat and faba bean products, and the levels and variation of enzyme activities present in the seeds.…”