Cereal Chem 59:418 - 422.  |  VIEW ARTICLE
Lipase Activity in Oat Flour Suspensions and Soluble Extracts.

G. J. Matlashewski, A. A. Urquhart, M. R. Sahasrabudhe, and I. Altosaar. Copyright 1982 by the American Association of Cereal Chemists, Inc. 

A radioisotope assay was developed for measuring lipase (triacyl glycerol acyl hydrolase) activity in aqueous suspensions of oat flour, with glycerol tri[1-14C]oleate as substrate. The pH optimum in 0.05M Tris-HCl buffer containing 1% (v/v) Triton-X-100 and 0.2% (v/v) benzene was 7.5; the temperature optimum was 35-39 C. Hydrolysis (followed as release of [1-14C]oleic acid) was linear for 8-10 min, with rates of 5-10 micro-mol of fatty acid released per minute per gram of flour. Triton-X-100 (0.5-2.0%) and benzene (0.2%) were essential for activity. Michaelis-Menton kinetics were exhibited with increasing concentrations of glycerol trioleate; the apparent Michaelis-Menton constant was 3.5mM. Lipase activities measured by this method and by colorimetric determination of free fatty acids released in oat flour doughs were comparable. A stable, active, soluble lipase extract was prepared from defatted oat flour by extraction in 0.05M Tris-HCl buffer (pH 7.5) containing 1% Triton-X-100. In a comparison of oats, wheat, barley, and rye, lipase activities in the ungerminated grains were 8.4, 0.7, 0.9, and 0.9 micro-mol of fatty acid released per minute per gram of flour, respectively. Rates in the grain germinated for two days were 11.9, 0.8, 0.6, and 3.2 micro-mol per minute per gram of flour, respectively.