Phospholipases of Leptospira. I. Presence of phospholipase A1 and lysophospholipase in Leptospira biflexa

The hydrolysis of phosphatidylethanolamine, phosphatidylcholine, lysophosphatidylcholine, and trioleoylglycerol by Leptospira biflexa strain Urawa was studied in vitro. Phospholipase A₁ was identified by the formation of ³²P- and ¹⁴C-labeled lyso-derivatives from ³²P-phosphatidylcholine, ³²P-phosphatidylethanolamine, or 1-acyl-2-1-¹⁴C]oleoyl-sn-glycero-3-phosphorylcholine. Phospholipase A₁ activity was independent of lipase in the microorganism since ¹⁴C-labeled trioleoylglycerol was scarcely attacked under the same conditions in which the phospholipids were hydrolyzed. Lysophospholipase activity was also demonstrated using ³²P- and non-labeled lysophosphatidylcholine. The activity of phospholipase A₁ was found in a broad range of pH but no optimal pH was determined. The pH optimum of lysophospholipase was 8.0. Both enzymes were labile to heat. Phospholipase C activity, however, could not be detected because no radioactive di- and monoacylglycerol was found in the experiment with 1-acyl-2-1-¹⁴C]-oleoyl-sn-glycero-3-phosphorylcholine as the substrate. It was inferred that phosphatidylethanolamine, which was the major component of phospholipids in leptospirae, was hydrolyzed serially by phospholipase A (A₁ and/or A₂?) and lysophospholipase to glycerophosphorylethanolamine via 2-acyl-type-lyso-derivative as one metabolic pathway of the substrate.