Open AccessPurified Methyl‐Coenzyme‐M Reductase is Activated when the Enzyme‐Bound Coenzyme F430 is Reduced to the Nickel(I) Oxidation State by Titanium(III) Citrate
Author(s) -
Goubeaud Marcel,
Schreiner Guido,
Thauer Rudolf K.
Publication year - 1997
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1997.00110.x
Subject(s) - cofactor , reductase , enzyme , chemistry , electron paramagnetic resonance , coenzyme a , stereochemistry , nickel , enzyme assay , biochemistry , organic chemistry , nuclear magnetic resonance , physics
The nickel porphinoid, coenzyme F430, is the prosthetic group of methyl‐coenzyme M reductase. The active form of the enzyme exhibits Ni‐EPR signals designated as MCR‐red1 and MCR‐red2. The inactive form of the enzyme is either EPR silent or it exhibits a distinct Ni‐EPR signal designated MCR‐0x1. Evidence is presented here that the MCR‐ox1 form of the enzyme can be converted in vitro to the MCR‐red1 form by reduction with titanium(III) citrate at pH 9. During conversion, the specific activity increases with increasing MCR‐red1 spin concentration from 2 U/mg to approximately 100 U/mg at spin concentrations higher than 80%. The reduced methyl‐coenzyme‐M reductase shows an ultraviolet/visible spectrum characteristic for coenzyme F430 in the Ni(I) oxidation state, with maxima at 386 nm and at 750 nm. The results indicate that methyl‐coenzyme‐M reductase is activated when the enzyme‐bound coenzyme F430 is reduced to the Ni(I) oxidation state. The experiments were performed with purified methyl‐coenzyme‐M reductase isoenzyme I of Methanobacterium thermoautotrophicum (strain Marburg).