Hydrolysis of phospholipids and glycerides by rat-liver preparations

Abstract

1. 1. Rat-liver homogenates were found to hydrolyze phospholipids, giving rise to both the 1-acyil and 2-acyl lysoderivatives. Subcellular fractionation of the homogenate separated the phospholipase A1 (specific for the I-acyl ester), the phospholipase A2 (specific for the 2-acyl ester) and the lysophospholipase(s) to a large extent. The phospholipase A1 was found to be located mainly in the microsomes, the phospholipase A2 in the mitochondria and the lysophospholipase(s) in the soluble fraction.

2. 2. Lipase activity, determined using sonicates of a triglyceride and phosphatidyl ethanolamine mixture, was found to be associated with the particulate fractions, mainly the mitochondrial fraction. The triglyceride on hydrolysis gave rise to free fatty acid and diglyceride.

3. 3. Studies using inhibitors and heat inactivation show that the phospholipase A2 requires metal ions, that the lipase is sensitive to p-chloromercuribenzoate and that the lysophospholipase(s) are sensitive to deoxycholate and heating.