Two genes control three alkaline phosphatases in Schizosaccharomyces pombe

Summary Mutants of Schizosaccharomyces pombe defective in alkaline phosphatase activity have been selected and analyzed. The mutations map in two different loci, pho2 and pho3, both located on the right arm of chromosome II. Pho2-mutants lack the activity of a soluble alkaline phosphatase specific for nitrophenyl-phosphate. Its activity requires Mg ions and it is abolished with Zn ions. The pho3-mutations block the activities of a soluble and of a membrane-bound nonspecific alkaline phosphatase. Both pho3-controlled enzyme forms exhibit similar substrate specificities, pH-optima and Mg ions are essential for both activities. Zn ions can partially replace the Mg ions. The three enzyme forms migrate differently on nondenaturing polyacrylamide gels. We speculate that pho2 and pho3 represent the structural genes for a substrate-specific and two forms of a nonspecific alkaline phosphatase.