Garny, SeikeVerschoor, Jan AdrianusGardiner, NeilJordaan, Justin2014-02-032014-02-032014-02Garny, S., Verschoor, J.A., Gardiner, N. & Jordaan, J. 2014, 'Spectrophotometric activity microassay for pure and recombinant cytochrome P450-type nitric oxide reductase', Analytical Biochemistry, vol. 447, no.1, pp. 23-29.0003-2697 (print)1096-0309 (online)10.1016/j.ab.2013.11.005http://hdl.handle.net/2263/33204Nitric oxide reductase (NOR) of the P450 oxidoreductase family accepts electrons directly from its cofactor, NADH, to reduce two nitric oxide (NO) molecules to one nitrous oxide molecule and water. The enzyme plays a key role in the removal of radical NO produced during respiratory metabolism, and applications in bioremediation and biocatalysis have been identified. However, a rapid, accurate, and sensitive enzyme assay has not yet been developed for this enzyme family. In this study, we optimized reaction conditions for the development of a spectrophotometric NOR activity microassay using NOC-5 for the provision of NO in solution. We also demonstrate that the assay is suitable for the quantification and characterization of P450-type NOR. The Km and kcat kinetic constants obtained by this assay were comparable to the values determined by gas chromatography, but with improved convenience and cost efficiency, effectively by miniaturization. To our knowledge, this is the first study to present the quantification of NOR activity in a kinetic microassay format.en© 2013 Elsevier Ltd. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Analytical Biochemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Analytical Biochemistry, vol. 447, no.1, pp. 23-29, 2014. doi : 10.1016/j.ab.2013.11.005Enzyme assayNADHNitric oxide reductase (NOR)Postprint Article