抄録
Enzymatic properties of a galactolipase (G-2) which has the highest activity in four galacto-lipases of rice bran were investigated. The molecular weight was estimated to be about 4×104 by gel filtration, and the Km value was 0.34mm for monogalactosyldiacylglycerol. The enzyme was activated markedly by sodium deoxycholate and slightly by calcium ion, but inhi-bited by EDTA, Triton-X-100, sodium dodecylsulfate, NaCl and organic solvents. The enzyme lost more than 95% of its original activity when heated at 50°C for 10min at pH 7.5. The enzyme catalyzed the hydrolysis of both galacto- and phospholipids. The relative hydrolysis rates decreased in the order of digalactosyldiacylglycerol>monogalactosylmono-acylglycerol>monogalactosyldiacylglycerol>lysophosphatidylcholine>phosphatidylcholine. The enzyme catalyzed the hydrolysis of fatty acid ester bonds at both C-1 and -2 positions of galactolipid. It is suggested that serine and cystine residues are important to the enzymic activity.
