Characterization of ceramide activated protein phosphatase: effect of cations

Sphiugohpids are becaning very importnat to our uncertanding of cell growth. Chferentiation, and apoptosis. Investigation of this bypotheis haidentified a sphingomyeling cycle, wlerey the action of a number of agoaist load is sphingortyelin aydroysis and ceranale genecation. Once geterated cearateide are throughia ceramide activated protem pho-phatade (CAPP)to dlich its dowtist team effects. Although, CAPP is a prime candidate for me diating cetamice signaling in mammalian cells. Its identily and its rennection to the down-tream targets of revamide activation remain eladive. Moleculat characterization of CAPP is therfore. a prelnde to a better inderstanding of the mechanist y which ceramide causes its downstream effects. our study demonstraten that at ImAl concentration some divaten cation, such as Mgappear to have a stimuarorv effect on both basal a CAPP phosphatase intivities. while others, such as Mn²⁺ and Zn²⁺, were inhibitony towards both phosphatase activities. Moreover, ather divalent cations werw lested and it was found that all were ingibitory towards CAPP activiy. On the contary monavalent cations had no effect on CAPP, inducd, they actnally stimulated basal phosphatase artivities. When EDTA and FGTA wree tested. It was observed that EDLA, dose dependently, abolished CAPP activity, while it had aecffect npon basal phosphatase activity. However. EGTA was much less protin in inhilating CAPP. From theae data, it is possible to condude that CAPP is a metal dependent protein and that the metal colactor is must Edely not Ca²⁺.