ABSTRACT
Sphingomyelinase catalyzes the hydrolysis of sphingomyelin to phosphorylcholine and ceramide [147]. Sphingomyelinase from Bacillus cereus was shown to possess at least two Mg2"1" binding sites with high and low affinities; the low affinity site is required for catalytic activity [148]. A model for the tertiary structure of this enzyme has been proposed [149], based on a protein fold recognition method; mutational studies of this enzyme are basically in agreement with this model. A catalytic mechanism of B. cereus sphingomyelinase has been proposed [148] that does not involve the magne sium cation. The exact function of Mg2+ in this interesting enzyme awaits a complete structural analysis.
