Production of inositol pentakisphosphate in a human T lymphocyte cell line

The human T lymphocyte cell line, Jurkat, produced five distinct water soluble, inositol-containing compounds following a period of labeling with 3H-myo-inositol and several hours of incubation in non-radioactive complete medium. The less polar four peaks had been previously shown to be inositol phosphates, InsP through InsP4. Here, we demonstrate that the prominent fifth, very polar, peak was inositol pentakisphosphate, InsP5. The pattern of incorporation of 3H-myo-inositol into InsP5 differed from that of incorporation into other inositol phosphates. InsP5, unlike the second messengers, InsP3 and InsP4, was not increased by perturbation of the T cell receptor/T3 complex.