Alkaline Phosphatase in Dictyostelium discoideum

Abstract

Several phosphatases have been demonstrated in Dictyostelium discoideum. The alkaline phosphatase, pH optimum 9·0, is a 5′-nucleotidase, attacking adenosine monophosphate and deoxyadenosine monophosphate, but catalyses also hydrolysis of p-nitrophenyl phosphate. In the absence of exogenous nutrients this enzyme increases about 6-fold in vitro during differentiation. Its activity in vivo may in part be controlled through endproduct inhibition by orthophosphate which has been found to accumulate in the cells during sporulation. Exogenous orthophosphate and glucose repress the levels of alkaline phosphatase in the spores. The data support the conclusion that end product inhibition and repression collaborate to ensure maximal alkaline phosphatase activity in vivo during culmination. Exogenous adenosine and deoxyadenosine increase the alkaline phosphatase levels in the sorocarps.