title: A particulate form of alkaline phosphatase in the yeast, Saccharomyces cerevisiae.
abstract: A new form of alkaline phosphatase (orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1) has been identified in the yeast Saccharomyces cerevisiae. Utilizing either synthetic or natural substrates, the enzyme exhibited a broad pH activity curve with maximum activity between 8.5 and 9.0. The enzyme was nonspecific with respect to substrate, attacking a variety of compounds containing phosphomonoester linkages, but has no detectable activity against polyphosphate, pyrophosphate or phosphodiester linkages. The enzyme exhibited an apparent Km of 0.25 mM with respect to p-nitrophenyl phosphate, 0.38 mM with respect to alpha-naphthyl phosphate, and 1.0 mM with respect to 5'AMP. The enzyme is regulated in a constitutive manner and its activity does not increase during phosphate starvation or sporulation, as does the repressible alkaline phosphatase. The enzyme is tightly bound to a particulate fraction of the cell, tentatively identified as the tonoplast membrane. It is not solubilized by treatment with high concentrations of NaCl, KH2PO4 or chaotropic agents. Triton X-100 (0.1%) solubilizes 12% of the particulate activity. This enzyme is differentiated from the other alkaline phosphatases found in yeast by its chromatographic elution DEAE-cellulose, kinetic parameters, heat stability and pH stability, as well as its particulate nature. This particulate alkaline phosphatase was found in every strain examined. It has a significantly lower specific activity in the phoH mutant and a higher activity in the acid phosphatase constitutive mutant A137.
mesh_terms: D000469:Alkaline Phosphatase / Q000302:isolation & purification / Q000378:metabolism*; D004355:Drug Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009154:Mutation; D010710:Phosphates / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013045:Species Specificity; D013172:Spores, Fungal / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D010710:Phosphates; D000469:Alkaline Phosphatase