The biochemical prerequisites for preventing pathogenic lysolecithin activity in the human gallbladder. II. Studies on the subcellular localization of lysophospholipase

Purification of an enzyme with lysophospholipase activity from rat intestinal mucosa by hydrophobic chromatography

A method based on hydrophobic chromatography is described for the purification of a lysophospholipase from the mucosa of rat small intestine. Under the conditions used, one single chromatographic run on phenyl-Sepharose CL-4B yielded a 582-fold purification with a 79% overall recovery of enzyme activity. A subsodium dodecyl sulphate gel electrophoresis; its isoelectric point is 5.6.

The prerequisites for local lysolecithin formation in the human gallbladder. II. Studies on the positional specificity of the phospholipase A activity

The positional specificity of the phospholipase A in human gallbladder epithelium was studied by using biosynthetically radioabeled diacylphosphoglycerides as substrates. Diacylphosphoglyceride in 14C-palmitic acid-labeled, autoclaved E.coli was hydrolyzed under the formation of monoacylphosphoglyceride and fatty acid that were both radiolabled. In contrast, diacylphosphoglyceride in 14C-oleate-labeled bacteria was hydrolyzed so as to give radiolabel in the fatty acid only. Since 14C-palmitate occupies predominantly the 1-acyl position and 14C oleate the 2-acyl position of the major E. coli diacylphosphoglycerides, these findings suggest that: 1) the phospholipase attacks and 2-position of diacylphosphoglycerides, and 2) a complete deacylation of diacylphosphoglycerides in the gallbladder wall is brought about by the combined action of phospholipase A2 and lysophospholipase, the latter being able to hydrolyze the 1-acyllysophosphoglyceride. It appears, therefore, that the biochemical preequisites for a local formation and degreadation of lysolecithin in the gallbladder itself are met by the positional specificity of theenzymes present. This finding further substantiates the hypothesis that lysolecithin is an adjustable mediator of aseptic cholecystitis.