Sphingoid bases and de novo ceramide synthesis: enzymes involved, pharmacology and mechanisms of action.
The sphingoid base backbones of sphingolipids (sphingosines, sphinganines, 4-hydroxysphinganines and others) are highly bioactive species directly and-in most cases-as their metabolites, the N-acyl-sphingoid bases (ceramides) and sphingoid base 1-phosphates. The complexity of these compounds affords many opportunities to prepare synthetic analogs for studies of sphingolipid metabolism and the functions of the sphingoid bases and metabolites. Described in this review are methods for the preparation of libraries of sphingoid bases, including a series of 1-deoxy-analogs, as well as information about their metabolism and biological activities. Findings with these compounds have uncovered some of the complications of working with compounds that mimic a naturally occurring biomodulator-such as that they are sometimes metabolized by enzymes that handle the endogenous compounds and the products may have potent (and unexpected) biological activities. Through studying such compounds, there is now a greater understanding of the metabolism and mechanism(s) of action of naturally occurring sphingoid bases as well as of these analogs.