title: The Ala-161-->Thr substitution in Escherichia coli alkaline phosphatase does not result in loss of enzymatic activity although the homologous mutation in humans causes hypophosphatasia.
abstract: The correlation between sequence homology and catalytic importance of a specific amino acid in the E. coli and Liver/Kidney/Bone (L/K/B) human alkaline phosphatase was investigated. For this reason Ala-161 in the E. coli enzyme was substituted with a threonine residue via site-specific mutagenesis. The homologous amino acid in the L/K/B alkaline phosphatase sequence has been shown to cause inactivation of the enzyme. In E. coli alkaline phosphatase the Ala-161-->Thr substitution results in a mutant enzyme with virtually unchanged catalytic properties when compared to the wild-type enzyme. Our results show that Ala-161 in the E. coli alkaline phosphatase does not have an important catalytic role. The results suggest that the three-dimensional topology of the L/K/B alkaline phosphatase may be different from that observed for the enzyme from E. coli.
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, MA 02167.
authors.forename: A
authors.initials: A
authors.lastname: Chaidaroglou
authors.forename: E R
authors.initials: ER
authors.lastname: Kantrowitz
mesh_terms: D000409:Alanine; D000469:Alkaline Phosphatase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D001842:Bone and Bones / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology*; D006801:Humans; D007014:Hypophosphatasia / Q000201:enzymology*; D007527:Isoenzymes / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D013912:Threonine
chemical_list: D007527:Isoenzymes; D011994:Recombinant Proteins; D013912:Threonine; D000469:Alkaline Phosphatase; D000409:Alanine