Lysophospholipase 1 in Trypanosoma brucei.

Protein fractions from Trypanosoma brucei brucei showed lysophospholipase 1 activity (E.E.3.1.1.5), against the substrate 1-acyl-sn-glycero-3-phosphocholine, and also phospholipase A1 activity (E.C.3.1.1.4) by hydrolysis of the 1-acyl bond of 1,2-diacyl-sn-glycero-3-phosphocholine. Both enzyme activities were eluted together and showed a 12-fold purification following Sephacryl S-200 column chromatography. A final 96-fold increase in activity was obtained by electrophoresis on nondenaturing polyacrylamide gels to yield a band containing both enzymic activities. Phospholipase A1 showed maximum activity between pH 6.0--8.5 and lysophospholipase 1 had a pH optimum of 8.5. Both activities were found mainly in the soluble fraction of disrupted trypanosomes and were similarly inhibited by N-ethylmaleimide and p-chloromercuribenzoic acid. Although Triton X-100 stimulated phospholipase A1 activity, it inhibited lysophospholipase 1 activity. The Km value for the lysophospholipase 1 was found to be 0.15 mM. It was not possible to resolve separate activities for lysophospholipase 1 and phospholipase A1 and the ratio of the two activities was approximately 1 : 10 for a variety of preparations and treatments. It is probable that a single enzyme displays both activities.