Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

Editor

Personal info

View

About

Terms

Javascript disabled

Please enable Javascript support in your browser to use this application.

Instructions on how to enable JavaScript on different browsers can be found here: http://www.google.com/support/bin/answer.py?answer=23852.

[edit this page]

Bolscher, B.G. et al.

A kinetic study of the reaction between human myeloperoxidase, hydroperoxides and cyanide. Inhibition by chloride and thiocyanate.

The reaction between myeloperoxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7), hydrogen peroxide and ethyl hydroperoxide was investigated using the stopped-flow technique. Like other peroxidases, myeloperoxidase forms two sequential peroxide compounds. The pH-dependence of the apparent second-order rate constant of compound I formation shows that there is an acid/base group on the enzyme with a pKa of 4.30 +/- 0.15, which - when protonated - prevents the reaction of the enzyme with peroxides. The rate constants for the formation of compound I by hydrogen peroxide and ethyl hydroperoxide are (2.3 +/- 0.1) X 10(7) M-1 X s-1 and (2.8 +/- 0.3) X 10(5) M-1 X s-1, respectively. The binding of cyanide to myeloperoxidase (k1 = (1.30 +/- 0.05) X 10(6) M-1 X s-1) is also regulated by an acid/base group with a pKa of 4.00 +/- 0.05 as is the case with hydrogen peroxide; also, only the protonated uncharged form of cyanide reacts with the enzyme. From their effects on the binding of cyanide to the enzyme it is concluded that chloride and thiocyanate bind to myeloperoxidase only when the acid/base group is protonated. The pH-dependence of the dissociation constant of the myeloperoxidase-chloride complex obtained from the spectral changes induced by chloride is the same as observed in the inhibition by chloride of the binding of cyanide. It is concluded that hydrogen peroxide, cyanide, chloride and thiocyanate bind at the same site on the enzyme.[1]

References

A kinetic study of the reaction between human myeloperoxidase, hydroperoxides and cyanide. Inhibition by chloride and thiocyanate. Bolscher, B.G., Wever, R. Biochim. Biophys. Acta (1984) [Pubmed]

Annotations and hyperlinks in this abstract are from individual authors of WikiGenes or automatically generated by the WikiGenes Data Mining Engine. The abstract is from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.About WikiGenes Open Access Licence Privacy Policy Terms of Use apsburg

The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.