Catalyzes the phosphorylation of sphingosine to form sphingosine-1-phosphate (S1P), which probably acts intracellularly as a second messenger perhaps by promoting cell proliferation. Overexpression of sgkA leads to increased growth rates on solid media and an increased resistance to the antitumor agents cisplatin and carboplatin. a sphingoid base + ATP = a sphingoid 1-phosphate + ADP + H(+) Inhibited by N,N,-dimethylsphingosine; this inhibitor increases sensitivity to cisplatin. Determined in cells overexpressing sgkA. Also appears enriched in some pseudopodia. 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.