Nickel-specific, slow-binding inhibition of carbon monoxide dehydrogenase from Rhodospirillum rubrum by cyanide

Journal Article · Tue Jun 13 00:00:00 EDT 1989 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00438a011· OSTI ID:5300847

Ensign, S A; Hyman, M R; Ludden, P W ^[1]

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1. Univ. of Wisconsin, Madison (USA)

The inhibition of purified carbon monoxide dehydrogenase from Rhodospirillum rubrum by cyanide was investigated in both the presence and absence of CO and electron acceptor. The inhibition was a time-dependent process exhibiting pseudo-first-order kinetics under both sets of conditions. The true second-order rate constants for inhibition were 72.2 M{sup {minus}1} s{sup {minus}1} with both substrates present and 48.9 and 79.5 M{sup {minus}1} s{sup {minus}1}, respectively, for the reduced and oxidized enzymes incubated with cyanide. CO partially protected the enzyme against inhibition after 25-min incubation with 100 {mu}M KCN. Dissociation constants of 8.46 {mu}M (KCN) and 4.70 {mu}M (CO) were calculated for the binding of cyanide and CO to the enzyme. Cyanide inhibition was fully reversible under an atmosphere of CO after removal of unbound cyanide. N{sub 2} was unable to reverse the inhibition. The competence of nickel-deficient (apo) CO dehydrogenase to undergo activation by NiCl{sub 2} was unaffected by prior incubation with cyanide. Cyanide inhibition of holo-CO dehydrogenase was not reversed by addition of NiCl{sub 2}. {sup 14}CN{sup {minus}} remained associated with holoenzyme but not with apoenzyme through gel filtration chromatography. These findings suggest that cyanide is a slow-binding, active-site-directed, nickel-specific, reversible inhibitor of CO dehydrogenase. The authors propose that cyanide inhibits CO dehydrogenase by being a analogue of CO and by binding through enzyme-bound nickel.

• DOE Contract Number: FG02-87ER13691
• OSTI ID: 5300847
• Journal Information: Biochemistry; (USA), Vol. 28:12; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CYANIDES
BIOLOGICAL EFFECTS
ENZYME INHIBITORS
BIOCHEMICAL REACTION KINETICS
OXIDOREDUCTASES
INHIBITION
CARBON 14 COMPOUNDS
CARBON MONOXIDE
NICKEL CHLORIDES
RHODOSPIRILLUM
TRACER TECHNIQUES
BACTERIA
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHLORIDES
CHLORINE COMPOUNDS
ENZYMES
HALIDES
HALOGEN COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MICROORGANISMS
NICKEL COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
TRANSITION ELEMENT COMPOUNDS
550201* - Biochemistry- Tracer Techniques