title: Catalytic properties and stability of three common variants of placental alkaline phosphatase.
abstract: Three placental alkaline phosphatases purified to homogeneity, i.e., the F, I, and S variants, were investigated for catalytic and stability properties. All three forms of the enzyme were found to have almost identical pH optima (10.7--10.8), similar sensitivity to the uncompetitive inhibitors L-phenylalanine (70%) and L-leucine (30%), and identical Km values against p-nitrophenylphosphate, beta-glycerophosphate, and alpha-naphthylphosphate. Significant differences among the three types were observed in thermal stability. The F variant was found to be most stable and the I variant most labile at 79 C. At 70 C all three forms were stable.
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics* / Q000378:metabolism; D003864:Depression, Chemical; D005260:Female; D014644:Genetic Variation; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007930:Leucine / Q000494:pharmacology; D010649:Phenylalanine / Q000494:pharmacology; D010920:Placenta / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D010649:Phenylalanine; D000469:Alkaline Phosphatase; D007930:Leucine