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.
National Center for Plant Genome Research, Jawaharlal Nehru University Campus, New Delhi 110067, India.
Subhra
S
Chakraborty
Niranjan
N
Chakraborty
Deepti
D
Jain
Dinakar M
DM
Salunke
Asis
A
Datta
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