Characterization and comparative analysis of Arabidopsis phosphatidylinositol phosphate 5-kinase 10 reveals differences in Arabidopsis and human phosphatidylinositol phosphate kinases

Arabidopsis phosphatidylinositol phosphate (PtdInsP) kinase 10 (AtPIPK10; At4g01190) is shown to be a functional enzyme of the subfamily A, type I AtPtdInsP kinases. It is biochemically distinct from AtPIPK1 (At1g21980), the only other previously characterized AtPtdInsP kinase which is of the B subfamily. AtPIPK10 has the same K-m, but a 10-fold lower V-max than AtPIPK1 and it is insensitive to phosphatidic acid. AtPIPKIO transcript is most abundant in inflorescence stalks and flowers, whereas A tPIPK1 transcript is present in all tissues. Comparative analysis of recombinant AtPIPKIO and AtPIPK1 with recombinant HsPIPKI alpha reveals that the Arabidopsi. s enzymes have roughly 200- and 20-fold lower V-max/K-m, respectively. These data reveal one explanation for the longstanding mystery of the relatively low phosphatidylinositol-(4,5)-bisphosphate:phosphatidylinositol-4-phosphate ratio in terrestrial plants. (c) 2005 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.