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GDP-mannose hydrolase (GDPMK), and similar proteins GDP-mannose hydrolase (GDPMK) is a NUDIX enzyme that uses GDP-mannose as the preferred substrate. It is distinct from Nudix ADP-ribose hydrolases. GDPMK and ADP-ribose pyrophosphatase seem to use similar catalytic mechanism. However, GDPMK hydrolysis does not rely on a single glutamate as the catalytic base; rather, it is dependent on residues that coordinate the magnesium ions and residues that position the substrate properly for catalysis. Members of the NUDIX hydrolase superfamily catalyze the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+, for their activity and contain a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which functions as a metal binding and catalytic site. Substrates of NUDIX hydrolases include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance & "house-cleaning" enzymes. Substrate specificity is used to define families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",