Active site geometry of oxalate decarboxylase from Flammulina velutipes: Role of histidine-coordinated manganese in substrate recognition.
Oxalate decarboxylase (OXDC) from the wood-rotting fungus Flammulina velutipes, which catalyzes the conversion of oxalate to formic acid and CO(2) 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 beta-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 hypothesized because all histidine knockout mutants showed total loss of decarboxylase activity. The atomic absorption spectroscopy analysis showed that OXDC contains Mn(2+) 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.
Chakraborty
Subhra
S
National Center for Plant Genome Research, Jawaharlal Nehru University Campus, New Delhi 110067, India.
Chakraborty
Niranjan
N
Jain
Deepti
D
Salunke
Dinakar M
DM
Datta
Asis
A
D000363:Agaricales / Q000201:enzymology*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002262:Carboxy-Lyases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D008670:Metals / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019815:Oxalic Acid / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D016415:Sequence Alignment
D008670:Metals; D008345:Manganese; D006639:Histidine; D019815:Oxalic Acid; D002262:Carboxy-Lyases; C021915:oxalate decarboxylase