Partial inactivation of cytochrome c oxidase by nonpolar mercurial reagents

Conference · Fri Jan 25 04:00:00 EST 1980 · J. Biol. Chem.; (United States)

OSTI ID:5408960

Mann, A J; Auer, H E

Purified beef heart cytochrome c oxidase is inactivated to the extent of 35 to 50% by the nonpolar mercurial reagents mercuric chloride and ethylmercuric chloride. The inactivation is complete within 5 min. In titrations of activity, the plateau level of inactivation is attained at added ethylmercuric chloride:heme a ratios of about 1:1. Up to 3 mercury atoms/heme a are bound to the oxidase, although only the first of these affects its enzymatic activity. Incubation of the ethylmercury-modified oxidase with sulfhydryl compounds reverses the inactivation, with 2,3-dimercaptopropanol being most effective of the reagents tested. Spectrophotometric and polarographic assays of enzymatic activity show that K/sub m/ values for the native and the ethylmercury-modified enzymes are practically indistinguishable, and that the partial inactivation observed for the latter is reflected exclusively in a lower value of V/sub max/ compared to that of the native enzyme. Based on these results, we propose that ethylmercuric chloride reacts with a single crucial--SH group per heme a, and that electron transfer processes in the modified product are partially inhibited.

• Research Organization: Univ. of Rochester School of Medicine, NY
• OSTI ID: 5408960
• Conference Information: Journal Name: J. Biol. Chem.; (United States) Journal Volume: 255:2
• Country of Publication: United States
• Language: English

Related Subjects

550201 -- Biochemistry-- Tracer Techniques
560305* -- Chemicals Metabolism & Toxicology-- Vertebrates-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMALS
BIOCHEMICAL REACTION KINETICS
CARBOXYLIC ACIDS
CATTLE
CHLORIDES
CHLORINE COMPOUNDS
CYTOCHROME OXIDASE
DOMESTIC ANIMALS
ELECTRON TRANSFER
ENZYME INHIBITORS
ENZYME REACTIVATION
ENZYMES
HALIDES
HALOGEN COMPOUNDS
HEME
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INHIBITION
KINETICS
MAMMALS
MERCURY CHLORIDES
MERCURY COMPOUNDS
MERCURY HALIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDASES
OXIDOREDUCTASES
PIGMENTS
PORPHYRINS
REACTION KINETICS
RUMINANTS
TOLERANCE
TOXICITY
VERTEBRATES