| Abstract
| - The neutral sphingomyelinases (N-SMases) are considered major candidates for mediatingthe stress-induced production of ceramide, and N-SMase activity has been identified, characterized, andcloned from bacteria, yeast, and mammalian cells. Although the level of identity between these enzymesis low, a number of key residues thought to be involved in metal binding and catalysis are conserved.This has led to the suggestion of a common catalytic mechanism, and thus, these enzymes are consideredto form an extended family of N-SMases. Despite considerable research into N-SMase activity in cellculture and various tissues, the lack, until recently, of molecular identification of specific N-SMase enzymeshad precluded specific insights into the regulation, physiological, and pathological roles of these proteins.In this review, we summarize, for the first time, current knowledge of the N-SMase family, focusing oncloned members from bacteria, yeast, and mammalian cells. We also briefly consider the major futuredirections for N-SMase research which promises highly significant and specific insight into sphingolipid-mediated functions.
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