Sphingomyelinase is part of the 'enterotoxin complex' produced by Bacillus cereus.

The three components of the 'enterotoxin complex' have been purified and the sequence of the first 14-15 amino acids of the proteins determined. Limited homology was found in the N-terminal sequence of the three proteins. The molecular mass of the proteins was determined to be 48, 40 and 34 kDa, respectively. Only the 40-kDa protein was toxic to Vero cells, whilst the 34-kDa protein was found to be hemolytic. The sequence of the first 14 N-terminal amino acids of this protein was identical to the sequence of the sphingomyelinase residues 28-41 (the N-terminal after loss of the signal sequence), except for a change from Gln to Glu in position 33 of the sphingomyelinase sequence.