The long form of sphingosine kinase 2 (Sphk2-L) is a species-specific isoform of the Sphk2 enzyme expressed in human but not in mouse. It is an N-terminal extended form of Sphk2, extended by 36 amino acids. It functions as expected, catalyzing the formation of sphingosine 1-phosphate from sphingosine, however it appears to have a decreased ability to inhibit DNA synthesis as compared to Sphk2-S (short form of Sphk2). Under normal cellular conditions, Sphk2-L does not appear to inhibit DNA synthesis, but under serum deprivation, SphK2-L translocates to the nucleus and accumlates. This accumlation may be involved in the cessation of cell proliferation or apoptosis depending on the cell type.