Oxidase, superoxide dismutase, and hydrogen peroxide reductase activities of methanobactin from types I and II methanotrophs.
Methanobactin (mb) is a copper-binding chromopeptide that appears to be involved in oxidation of methane by the membrane-associated or particulate methane monooxygenase (pMMO). To examine this potential physiological role, the redox and catalytic properties of mb from three different methanotrophs were examined in the absence and presence of O(2). Metal free mb from the type II methanotroph Methylosinus trichosporium OB3b, but not from the type I methanotrophs Methylococcus capsulatus Bath or Methylomicrobium album BG8, were reduced by a variety of reductants, including NADH and duroquinol, and catalyzed the reduction of O(2) to O(2)(-). Copper-containing mb (Cu-mb) from all three methanotrophs showed several interesting properties, including reductase dependent oxidase activity, dismutation of O(2)(-) to H(2)O(2), and the reductant dependent reduction of H(2)O(2) to H(2)O. The superoxide dismutase-like and hydrogen peroxide reductase activities of Cu-mb were 4 and 1 order(s) of magnitude higher, respectively, than the observed oxidase activity. The results demonstrate that Cu-mb from all three methanotrophs are redox-active molecules and oxygen radical scavengers, with the capacity to detoxify both superoxide and hydrogen peroxide without the formation of the hydroxyl radicals associated with Fenton reactions. As previously observed with Cu-mb from Ms. trichosporium OB3b, Cu-mb from both type I methanotrophs stimulated pMMO activity. However, in contrast to previous studies using mb from Ms. trichosporium OB3b, pMMO activity was not inhibited by mb from the two type I methanotrophs at low copper to mb ratios.
Choi
Dong W
DW
Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, 4164 Molecular Biology Building, Ames, IA 50011-3211, USA.
Semrau
Jeremy D
JD
Antholine
William E
WE
Hartsel
Scott C
SC
Anderson
Ryan C
RC
Carey
Jeffrey N
JN
Dreis
Ashley M
AM
Kenseth
Erik M
EM
Renstrom
Joel M
JM
Scardino
Lori L
LL
Van Gorden
Garrett S
GS
Volkert
Anna A
AA
Wingad
Aaron D
AD
Yanzer
Paul J
PJ
McEllistrem
Marcus T
MT
de la Mora
Arlene M
AM
DiSpirito
Alan A
AA
D002384:Catalysis; D016166:Free Radical Scavengers; D006861:Hydrogen Peroxide / Q000378:metabolism; D007093:Imidazoles / Q000378:metabolism*; D020619:Methylococcus capsulatus / Q000201:enzymology*; D020602:Methylosinus trichosporium / Q000201:enzymology*; D009842:Oligopeptides / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D010105:Oxygenases; D010544:Peroxidases; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
D016166:Free Radical Scavengers; D007093:Imidazoles; D009842:Oligopeptides; C491147:methanobactin; D013481:Superoxides; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D010544:Peroxidases; D010105:Oxygenases; C021555:methane monooxygenase; D013482:Superoxide Dismutase