A major breakthrough came in the mid-1980s with the cloning of the first N-SMases from "Bacillus cereus" and "Staphylococcus aureus". Using the sequences of these bacterial sphingomyelinases in homology searches ultimately led to the identification of the yeast N-SMases ISC1 in the budding yeast "Saccharomyces cerevisiae" and the mammalian N-SMase enzymes, nSMase1 and nSMase2. The identity between mammalian, yeast and bacterial SMases is very low - being approximately 20% between nSMase2 and the B. cereus SMase. However, an alignment of the sequences (see figure) indicate a number of conserved residues throughout the family, particularly in the catalytic region of the enzymes. This has led to the suggestion of a common catalytic mechanism for the N-SMase family.