Peroxidase-catalyzed S-oxygenation: Mechanism of oxygen transfer for lactoperoxidase

Journal Article · Tue Sep 17 04:00:00 EDT 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00101a007· OSTI ID:5702833

Doerge, D R; Cooray, N M ^[1]; Brewster, M E ^[2]

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1. Univ. of Hawaii, Honolulu (United States)
2. Pharmatec Inc., Alachua, FL (United States)

The mechanism of organosulfur oxygenation by peroxidases (lactoperoxidase (LPX), chloroperoxidase, thyroid peroxidase, and horseradish peroxidase) and hydrogen peroxide was investigated by use of para-substituted thiobenzamides and thioanisoles. The rate constants for thiobenzamide oxygenation by LPX/H{sub 2}O{sub 2} were found to correlate with calculated vertical ionization potentials, suggesting rate-limiting single-electron transfer between LPX compound I and the organosulfur substrate. The incorporation of oxygen from {sup 18}O-labeled hydrogen peroxide, water, and molecular oxygen into sulfoxides during peroxidase-catalyzed S-oxygenation reactions was determined by LC- and GC-MS. All peroxidases tested catalyzed essentially quantitative oxygen transfer from {sup 18}O-labeled hydrogen peroxide into thiobenzamide S-oxide, suggesting that oxygen rebound from the oxoferryl heme is tightly coupled with the initial electron transfer in the active site. Experiments using H{sub 2}{sup 18}O{sub 2}, and H{sub 2}{sup 18}O showed the LPX catalyzed approximately 85,22, and 0% {sup 18}O-incorporation into thioanisole sulfoxide oxygen, respectively. These results are consistent with an active site controlled mechanism in which the protein radical form of LPX compound I is an intermediate in LPX-mediated sulfoxidation reactions.

• OSTI ID: 5702833
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 30:37; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
BIOCHEMISTRY
CHEMISTRY
ENZYMES
EVEN-EVEN NUCLEI
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
ISOTOPES
LIGHT NUCLEI
NUCLEI
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDOREDUCTASES
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PEROXIDASES
PEROXIDES
PROTEINS
STABLE ISOTOPES
SULFOXIDES
UPTAKE