Appearance of triacylglycerol lipase in egg yolk sac of Japanese quail during embryonic development, its partial purification and some properties

Triacylglycerol lipase activity appeared on the 8th day of embryonic development of the Japanese quail in the egg yolk sac and its contents, and activity was highest on the 12th day, although yolk lipids decreased markedly at the later stage of embryonic development. We extracted the lipase from the defatted yolk sac of 12-day eggs, purified it to a 200-fold specific activity. This purified preparation gave at least 2 bands having hydrolyzing activity against β-naphthylbutyrate upon polyacrylamide gel electrophoresis, with molecular weights of 55,000 and 57,000. The enzyme had maximum activity at pH 8.0 and 38°C. Concerning substrate specificity, the enzyme hydrolyzed a variety of triglycerides, but had the highest specificity for tributyrin. This lipase had some heterogenous forms on isoelectric focusing, with pI values of 4.8 to 5.2. The profile of isoelectric focusing was changed by neuraminidase treatment, showing that sialic acid content affects the net charge of the lipase molecules.