Browsing by Author "Salunke, Dinakara M"

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    Active site geometry of oxalate decarboxylase from Flammulina velutipes: Role of histidine coordinated manganese in substrate recognition
    (Cold Spring Harbor Laboratory Press, 2002) Chakraborty, Subhra; Chakraborty, Niranjan; Jain, Deepti; Salunke, Dinakara M; Datta, Asis
    Oxalate decarboxylase (OXDC) from the wood-rotting fungus Flammulina velutipes, which catalyzes the conversion of oxalate to formic acid and CO2 in a single-step reaction, is a duplicated double-domain germin family enzyme. It has agricultural as well as therapeutic importance. We reported earlier the purification and molecular cloning of OXDC. Knowledge-based modeling of the enzyme reveals a ␤-barrel core in each of the two domains organized in the hexameric state. A cluster of three histidines suitably juxtaposed to coordinate a divalent metal ion exists in both the domains. Involvement of the two histidine clusters in the catalytic mechanism of the enzyme, possibly through coordination of a metal cofactor, has been hypoth- esized because all histidine knockout mutants showed total loss of decarboxylase activity. The atomic absorption spectroscopy analysis showed that OXDC contains Mn2+ at up to 2.5 atoms per subunit. Docking of the oxalate in the active site indicates a similar electrostatic environment around the substrate-binding site in the two domains. We suggest that the histidine coordinated manganese is critical for substrate recognition and is directly involved in the catalysis of the enzyme.