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Title: Structural and spectroscopic characterisation of a heme peroxidase from sorghum
Authors: Nnamchi, Chukwudi I.
Parkin, Gary
Efimov, Igor Igor
Basran, Jaswir
Kwon, Hanna
Svistunenko, Dimitri A.
Agirre, Jon
Okolo, Bartholomew N.
Moneke, Anene
Nwanguma, Bennett C.
Moody, Peter C. E.
Raven, Emma L.
First Published: 14-Dec-2015
Publisher: Springer Verlag
Citation: Journal of Biological Inorganic Chemistry, 2016, 21 (1), pp. 63-70
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.
DOI Link: 10.1007/s00775-015-1313-z
ISSN: 0949-8257
eISSN: 1432-1327
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © the authors, 2015. This is an open-access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Appears in Collections:Published Articles, Dept. of Molecular and Cell Biology

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