Purification and properties of zinc-metallophospholipase C from Pseudomonas fluorescens

Phospholipase C produced by Pseudomonas fluorescens, isolated as a laboratory contaminant, has been purified to apparent homogeneity by ammonium sulphate fractionation, anion-exchange and size-exclusion chromatographies. The apparent molecular mass of the purified polypeptide was 39.5 kDa. Purified preparations of phospholipase C were used to characterize its enzymic properties and to obtain amino acid sequence of the N-terminus of the molecule. The P. fluorescens phospholipase C hydrolysed PtdEtn, PtdCho and PtdSer (PtdEtn > PtdCho >> PtdSer) and was relatively thermostable. The enzyme was inactivated in the presence of chelating agent o-phenanthroline and the activity restored after addition of zinc. Properties of this enzyme and in particular the requirement for zinc ions for the activity, revealed similarity with the well characterised Bacillus cereus phospholipase C. Similarities with other bacterial and mammalian enzymes reported to be related to the B. cereus type are discussed.