title: A novel GDP-mannose mannosyl hydrolase shares homology with the MutT family of enzymes.
abstract: The product of the Escherichia coli orf1.9, or yefc, gene (GenBank accession number L11721) has been expressed under the control of a T7 promoter, purified to apparent homogeneity, and identified as a novel enzyme that hydrolyzes GDP-mannose or GDP-glucose to GDP and the respective hexose. The enzyme has little or no activity on other nucleotides, dinucleotides, nucleotide sugars, or sugar phosphates. It has a pH optimum between 9.0 and 9.5, a Km of 0.3 mM, and a Vmax of 1.6 mumol min-1 mg-1 for GDP-mannose, and it requires divalent cations for activity. This enzyme of 160 amino acids (M(r) = 18, 405) contains the consensus sequence GX(I/L/V)(E/Q)(X)2ET(X)6R(X)4E(X)2(I/L), characteristic of the MutT family of proteins and previously shown to form part of the nucleotide-binding site of MutT (Frick, D. N., Weber, D. J., Abeygunawardana, C., Gittis, A. G., Bessman, M. J., and Mildvan, A. S. (1995) Biochemistry 34, 5577-5586). A comparison of the enzymatic reactions catalyzed by the GDP-mannose mannosyl hydrolase and the other enzymes of the MutT family suggests that the consensus signature sequence designates a novel nucleoside diphosphate binding site and catalytic motif.
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: D N
authors.initials: DN
authors.lastname: Frick
authors.forename: B D
authors.initials: BD
authors.lastname: Townsend
authors.forename: M J
authors.initials: MJ
authors.lastname: Bessman
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000737:chemistry / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D017931:DNA Primers; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011755:Pyrophosphatases; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; D010744:Phosphoric Monoester Hydrolases; D006026:Glycoside Hydrolases; C096402:yefc protein, E coli; D011755:Pyrophosphatases; C052211:mutT protein, E coli