Multiple phospholipid substrates of phospholipase C/sphingomyelinase HR2 from Pseudomonas aeruginosa

Abstract The activity of phospholipase C/sphingomyelinase HR 2 (PlcHR 2 ) from Pseudomonas aeruginosa was characterized on a variety of substrates. The enzyme was assayed on liposomes (large unilamellar vesicles) composed of PC:SM:Ch:X (1:1:1:1; mol ratio) where X could be PE, PS, PG, or CL. Activity was measured directly as disappearance of substrate after TLC lipid separation. Previous studies had suggested that PlcHR 2 was active only on PC or SM. However we found that, of the various phospholipids tested, only PS was not a substrate for PlcHR 2 . All others were degraded, in an order of preference PC > SM > CL > PE > PG. PlcHR 2 activity was sensitive to the overall lipid composition of the bilayer, including non-substrate lipids.