Catalyzes the phosphorylation of sphingosine to form sphingosine-1-phosphate (S1P), which probably acts intracellularly as a second messenger perhaps by promoting cell proliferation. a sphingoid base + ATP = a sphingoid 1-phosphate + ADP + H(+) Inhibited by N,N,-dimethylsphingosine. Cells grow more slowly on solid media and are more sensitive than wild-type to the antitumor agents cisplatin and carboplatin; both effects are exacerbated in sgkA and sgkB double knockout. Exogenous S1P reverses the sensitivity to cisplatin.