Universität zu Köln

Kalimuthu, Palraj, Belaidi, Abdel A., Schwarz, Guenter ORCID: 0000-0002-2118-9338 and Bernhardt, Paul V. (2017). Chitosan-Promoted Direct Electrochemistry of Human Sulfite Oxidase. J. Phys. Chem. B, 121 (39). S. 9149 - 9160. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-6106

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Abstract

Direct electrochemistry of human sulfite oxidase (HSO) has been achieved on carboxylate-terminated self-assembled monolayers cast on a Au working electrode in the presence of the promoter chitosan. The modified electrode facilitates a well-defined nonturnover redox response from the heme cofactor (Fe-III/II) in 750 mM Tris, MOPS, and bicine buffer solutions. The formal redox potential of the nonturnover response varies slightly depending on the nature of the thiol monolayer on the Au electrode. Upon addition of sulfite to the cell a pronounced catalytic current from HSO-facilitated sulfite oxidation is observed. The measured catalytic rate constant (k(cat)) is around 0.2 s(-1) (compared with 26 s(-1) obtained from solution assays), which indicates that interaction of the enzyme with the electrode lowers overall catalysis although native behavior is retained in terms of substrate concentration dependence, pH dependence, and inhibition effects. In contrast, no catalytic activity is observed when HSO is confined to amine-terminated thiol monolayers although well-defined noncatalytic responses from the heme cofactor are still observed. These differences are linked to flexibility of HSO, which can switch between active and inactive conformations, and also competitive ion exchange processes at the electrode surface involving the enzyme and substrate.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Kalimuthu, Palraj UNSPECIFIED UNSPECIFIED UNSPECIFIED Belaidi, Abdel A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schwarz, Guenter UNSPECIFIED orcid.org/0000-0002-2118-9338 UNSPECIFIED Bernhardt, Paul V. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-214518
DOI:	10.1021/acs.jpcb.7b06712
Journal or Publication Title:	J. Phys. Chem. B
Volume:	121
Number:	39
Page Range:	S. 9149 - 9160
Date:	2017
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	1520-6106
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Biochemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language INTRAMOLECULAR ELECTRON-TRANSFER; MOLYBDENUM COFACTOR DEFICIENCY; INDIUM TIN OXIDE; CATALYTIC VOLTAMMETRY; CYTOCHROME-C; OXIDIZING ENZYMES; MOLECULAR-WEIGHT; DEHYDROGENASE; KINETICS; PROTEIN Multiple languages Chemistry, Physical Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/21451