Sulfoxidation mechanism of vanadium bromoperoxidase from Ascophyllum nodosum. Evidence for direct oxygen transfer catalysis.
We have previously shown that vanadium bromoperoxidase from Ascophyllum nodosum mediates production of the (R)-enantiomer of methyl phenyl sulfoxide with 91% enantiomeric excess. Investigation of the intrinsic selectivity of vanadium bromoperoxidase reveals that the enzyme catalyzes the sulfoxidation of methyl phenyl sulfide in a purely enantioselective manner. The K(m) of the enzyme for methyl phenyl sulfide was determined to be approximately 3.5 mM in the presence of 25% methanol or tert-butanol. The selectivity of the sulfoxidation of methyl phenyl sulfide is optimal in the temperature range 25-30 degrees C and can be further optimized by increasing the enzyme concentration, yielding selectivities with up to 96% enantiomeric excess. Furthermore, we established for the first time that vanadium bromoperoxidase is functional at temperatures up to 70 degrees C. A detailed investigation of the sulfoxidation activity of this enzyme using (18)O-labeled hydrogen peroxide shows that vanadium bromoperoxidase mediates the direct transfer of the peroxide oxygen to the sulfide. A schematic model of the vanadium haloperoxidase sulfoxidation mechanism is presented.
ten Brink
H B
HB
E.C. Slater Institute, BioCentrum, University of Amsterdam, the Netherlands.
Schoemaker
H E
HE
Wever
R
R
D002384:Catalysis; D008968:Molecular Conformation; D010100:Oxygen / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D000459:Phaeophyceae / Q000201:enzymology; D012624:Seaweed / Q000201:enzymology*; D013379:Substrate Specificity; D013440:Sulfides / Q000378:metabolism*
D013440:Sulfides; C093850:methylphenylsulfide; D010544:Peroxidases; C026195:bromide peroxidase; D010100:Oxygen