A p32-sphingosine-activated protein kinase responds to low concentrations of D-erythro-Sphingosine with an initial activation observed at 2.5 μM and a peak activity at 10-20 μM. This kinase shows a modest specificity for D-erythro-Sphingosine over other sphingosine tereoisomers, and a preference for sphingosines over ihydrosphingosines. D-erythro-Sphingosine inhibits protein kinase C in vitro. D-erythro-Sphingosine has been shown to inhibit protein kinase C, which affects cell regulation and several signal transduction pathways, and exhibits antitumor promoter activities in various mammalian cells.