Download MendeleyStructural and Spectroscopic Characterisation of a Heme Peroxidase from Sorghum.
Nnamchi, C.I., Parkin, G., Efimov, I., Basran, J., Kwon, H., Svistunenko, D.A., Agirre, J., Okolo, B.N., Moneke, A., Nwanguma, B.C., Moody, P.C.E., Raven, E.L.(2016) J Biol Inorg Chem 21: 63
- PubMed: 26666777 Search on PubMedSearch on PubMed Central
- DOI: https://doi.org/10.1007/s00775-015-1313-z
- Primary Citation Related Structures:
5AOG - PubMed Abstract:
A cationic class III peroxidase from Sorghum bicolor was purified to homogeneity. The enzyme contains a high-spin heme, as evidenced by UV-visible spectroscopy and EPR. Steady state oxidation of guaiacol was demonstrated and the enzyme was shown to have higher activity in the presence of calcium ions. A Fe(III)/Fe(II) reduction potential of -266 mV vs NHE was determined. Stopped-flow experiments with H2O2 showed formation of a typical peroxidase Compound I species, which converts to Compound II in the presence of calcium. A crystal structure of the enzyme is reported, the first for a sorghum peroxidase. The structure reveals an active site that is analogous to those for other class I heme peroxidase, and a substrate binding site (assigned as arising from binding of indole-3-acetic acid) at the γ-heme edge. Metal binding sites are observed in the structure on the distal (assigned as a Na(+) ion) and proximal (assigned as a Ca(2+)) sides of the heme, which is consistent with the Ca(2+)-dependence of the steady state and pre-steady state kinetics. It is probably the case that the structural integrity (and, thus, the catalytic activity) of the sorghum enzyme is dependent on metal ion incorporation at these positions.
- Department of Microbiology, University of Nigeria, Nsukka, Nigeria.
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