title: Phospholipase C from Bacillus cereus has sphingomyelinase activity.
abstract: Purified, electrophoretically homogeneous phospholipase C (PLC) preparations can be separated into two peaks by isoelectric focusing in sucrose gradients. The main peak has an isoelectric pH of 6.6-6.8 and contains two Zn2+ per molecule. The more acid peak (isoelectric pH about 6.2) contains about one Zn2+ per molecule and has a markedly reduced specific activity which can be raised by adding Zn2+. The purified enzyme has a low sphingomyelinase activity which coincides completely with the lecithinase activity in fractions from isoelectric focusing. The sphingomyelinase activity was greatly enhanced by substitution of Co2+ for Zn2+ but remained essentially unaltered when the levels of Ca2+ and Mg2+ were changed. These findings provide evidence that the sphingomyelinase activity is a true endogenous activity of PLC and not caused by contaminating sphingomyelinase.
mesh_terms: D001409:Bacillus cereus / Q000201:enzymology*; D007525:Isoelectric Focusing; D010740:Phospholipases / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism*; D010738:Type C Phospholipases / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D010740:Phospholipases; D010727:Phosphoric Diester Hydrolases; D010738:Type C Phospholipases; D013108:Sphingomyelin Phosphodiesterase