title: Biosynthesis of acid phosphatase of baker's yeast. Characterization of a protoplast-bound fraction containing precursors of the exo-enzyme.
abstract: 1. Yeast protoplasts, secreting acid phosphatase (orthophosphoric-monoester phosphohydrolase (acid optimum) EC 3.1.3.2) contain a small amount of firmly bound enzyme, even after lysis (Van Rijn, H.J.M., Boer, P. and Steyn-Parvé, E.P. (1972) Biochim. Biophys. Acta 268, 431-441). The major part (70%) of this protoplast-bound acid phosphatase can be solubilized by nonionic detergents, such as Triton X-100. 2. The kinetics of radioactive amino acid incorporation in the solubilized and in the secreted enzyme has been estimated by pulse-chase labelling of secreting protoplasts, followed by fractionation and counting radioactivity in the enzyme band in polyacrylamide gels after electrophoresis at pH 5.0. A precursor-product relationship between the Triton X-100-extractable fraction of the protoplast-bound acid phosphatase and the secreted enzyme is apparent. 3. The solubilized acid phosphatase is essentially indistinguishable from the secreted enzyme with regard to a number of enzymatic properties and its stability towards pH and temperature. Both enzymes also behave alike on polyacrylamide-gel electrophoresis, producing a single acid phosphatase band with glycoprotein character and comparable mobility. 4. A striking difference is seen in isopycnic equilibrium sedimentation in CsCl: the secreted acid phosphatase is homogeneous, with a buoyant density of p equals 1.47 g/cm3, while the Triton X-100-extractable part of the protoplast-bound acid phosphatase is heterogeneous; besides heavier material a major component with buoyant density of p equals 1.37 g/cm3 is always visible.
mesh_terms: D000135:Acid Phosphatase / Q000096:biosynthesis* / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D004355:Drug Stability; D004591:Electrophoresis, Polyacrylamide Gel; D004792:Enzyme Precursors / Q000096:biosynthesis*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011485:Protein Binding; D011523:Protoplasts / Q000201:enzymology*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D012995:Solubility; D013696:Temperature; D013997:Time Factors
chemical_list: D000596:Amino Acids; D004792:Enzyme Precursors; D000135:Acid Phosphatase