NDLI: Anaerobic Oxidation-Reduction Titrations of Fungal Laccase EVIDENCE FOR SEVERAL HIGH POTENTIAL ELECTRON-ACCEPTING SITES

Content Provider	Journal of Biological Chemistry (JBC)
Author	Fee, James A. Malkin, Richard Malmström, Bo G. Vännga°rd, Tore
Abstract	Anaerobic oxidation-reduction titrations of fungal laccase with the reducing agents octacyanotungstate(IV), hexacyanoferrate(II), quinol, and ascorbate have been performed by optical and electron paramagnetic resonance (EPR) spectroscopy. With the high potential reducing agent (0.5 volt), octacyanotungstate(IV), 3.7 electron equivalents are required to reduce the "blue" Cu2+ (type 1) in the protein and the blue color is found to decrease linearly with the amount of titrant added. No additional reducing equivalents can be taken up by the protein at this oxidation-reduction level. Similar results are obtained with the other reducing agents with regard to the number of electron equivalents necessary to reduce the type 1 Cu2+.EPR measurements during the titrations have confirmed that the type 1 Cu2+ is an electron-accepting site. These measurements have also shown that the "non-blue" Cu2+ (type 2) behaves as a heterogeneous species with respect to its reducibility by all substrates. No unusual EPR signal appears during the course of the oxidation-reduction titrations of laccase.From these results, it is concluded that the type 1 Cu2+ and two additional electron-accepting sites are reduced in a "cooperative" manner but the involvement of the type 2 Cu2+ could not be defined. It is suggested on the basis of these results that the most likely candidates for the two additional high potential electron-accepting sites in laccase are the two diamagnetic copper atoms in the molecule and that these copper atoms would have to be present as a Cu2+-Cu2+ pair in the native molecule.
Related Links	http://www.jbc.org/content/244/15/4200.abstract
Ending Page	4207
Starting Page	4200
Page Count	8
File Format	HTM / HTML PDF
ISSN	00219258
Journal	Journal of Biological Chemistry (JBC)
Issue Number	15
Volume Number	244
e-ISSN	1083351X
Language	English
Publisher	American Society for Biochemistry and Molecular Biology
Publisher Date	1969-08-10
Access Restriction	Open
Subject Keyword	OXIDATION-REDUCTION AND BIOENERGETICS
Alternative Title	Anaerobic Oxidation-Reduction Titrations of Fungal Laccase
Content Type	Text
Resource Type	Article
Subject	Cell Biology Biochemistry Molecular Biology

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