Kinetic characterization of the carbon monoxide-acetyl-CoA (carbonyl group) exchange activity of the acetyl-CoA synthesizing CO dehydrogenase from Clostridium thermoaceticum

Journal Article · Tue Oct 04 04:00:00 EDT 1988 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00420a019· OSTI ID:6897662

Raybuck, S A; Bastian, N R; Orme-Johnson, W H; Walsh, C T ^[1]

---

1. Massachusetts Institute of Technology, Cambridge (USA)

CO dehydrogenase from Clostridium thermoaceticum is a nickel-containing enzyme that catalyzes both the reversible conversion of CO{sub 2} to CO (for incorporation into the carbonyl group of acetate) and the synthesis of acetyl-CoA from methyl corrinoid, CO, and CoASH. The latter activity is conveniently assayed by monitoring the exchange of (1-{sup 14}C)acetyl-CoA (carbonyl group) with {sup 12}CO. Kinetic parameters for the highly oxygen sensitive exchange activity have been determined. In addition, coenzyme A analogues have been tested as inhibitors of the exchange to probe the active site of the enzyme; each has no effect on the CO{sub 2} {rightleftharpoons} CO activity of CO dehydrogenase. Coenzyme A, the substrate for acetate biosynthesis, is a potent competitive inhibitor. Comparison of this value with that for desulfo-CoA suggests that a key mode of binding is through the sulfur atom, possibly to a metal site on the enzyme. The relatively high affinity of the enzyme for CoASH relative to acetyl-CoA is consistent with its proposed operation in the acetogenic direction. The differential sensitivity to oxygen and storage of the two activities of CO dehydrogenase as well as the contrasting effect of coenzyme A inhibitors suggest that acetate assemblage occurs at a site distinct from that for CO dehydrogenation.

• OSTI ID: 6897662
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 27:20; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACETATES
BACTERIA
BIOCHEMICAL REACTION KINETICS
CARBON 12
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CARBON ISOTOPES
CARBON MONOXIDE
CARBON OXIDES
CARBOXYLIC ACID SALTS
CHALCOGENIDES
CHROMATOGRAPHY
CLOSTRIDIUM
COENZYMES
ENZYME ACTIVITY
ENZYMES
EVEN-EVEN NUCLEI
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
LIQUID COLUMN CHROMATOGRAPHY
MICROORGANISMS
MOLECULAR STRUCTURE
NUCLEI
OXIDES
OXIDOREDUCTASES
OXYGEN COMPOUNDS
REACTION KINETICS
SEPARATION PROCESSES
STABLE ISOTOPES