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Structural and enzymatic characterization of human recombinant GDP‐ D ‐mannose‐4,6‐dehydratase
Author(s) -
Bisso Angela,
Sturla Laura,
Zanardi Davide,
De Flora Antonio,
Tonetti Michela
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00982-5
Subject(s) - dehydratase , enzyme , biochemistry , mannose , complementary dna , biosynthesis , recombinant dna , biology , escherichia coli , fucose , enzyme kinetics , chemistry , glycoprotein , active site , gene
GDP‐ D ‐mannose‐4,6‐dehydratase (GMD) is the key enzyme in the ‘de novo’ pathway of GDP‐ L ‐fucose biosynthesis. The reported cDNA sequences for human GMD predict three forms of different length, whose ‘in vivo’ occurrence and molecular properties are completely undefined. Here, we report the expression in Escherichia coli and the properties of each native recombinant GMD form. Only the 42 kDa long GMD (L‐GMD) and the 40.2 kDa (M‐GMD) forms were recovered as soluble functional proteins, while the 38.7 kDa form, short GMD (S‐GMD), lacking an N‐terminal domain critical for dinucleotide binding, was inactive and formed a precipitate. Both L‐GMD and M‐GMD are homodimers and contain 1 mol of tightly bound NADP + . Their kinetic properties ( K m , K cat ) are apparently identical and both forms are non‐competitively feedback‐inhibited by GDP‐ L ‐fucose to a similar extent. M‐GMD is the predominant enzyme form expressed in several human cell lines. These data seem to suggest that modulation of the ‘de novo’ pathway of GDP‐ L ‐fucose biosynthesis involves mechanisms other than differential ‘in vivo’ expression of GMD forms.