Demonstration of carbon-carbon bond cleavage of acetyl coenzyme A by using isotopic exchange catalyzed by the CO dehydrogenase complex from acetate-grown Methanosarcina thermophila.
The purified nickel-containing CO dehydrogenase complex isolated from methanogenic Methanosarcina thermophila grown on acetate is able to catalyze the exchange of [1-14C] acetyl-coenzyme A (CoA) (carbonyl group) with 12CO as well as the exchange of [3'-32P]CoA with acetyl-CoA. Kinetic parameters for the carbonyl exchange have been determined: Km (acetyl-CoA) = 200 microM, Vmax = 15 min-1. CoA is a potent inhibitor of this exchange (Ki = 25 microM) and is formed under the assay conditions because of a slow but detectable acetyl-CoA hydrolase activity of the enzyme. Kinetic parameters for both exchanges are compared with those previously determined for the acetyl-CoA synthase/CO dehydrogenase from the acetogenic Clostridium thermoaceticum. Collectively, these results provide evidence for the postulated role of CO dehydrogenase as the key enzyme for acetyl-CoA degradation in acetotrophic bacteria.
Raybuck
S A
SA
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts.
Ramer
S E
SE
Abbanat
D R
DR
Peters
J W
JW
Orme-Johnson
W H
WH
Ferry
J G
JG
Walsh
C T
CT
D000085:Acetates / Q000378:metabolism*; D000105:Acetyl Coenzyme A / Q000378:metabolism*; D000445:Aldehyde Oxidoreductases / Q000378:metabolism*; D002250:Carbon Radioisotopes; D019605:Euryarchaeota / Q000201:enzymology* / Q000254:growth & development; D007700:Kinetics; D009097:Multienzyme Complexes / Q000378:metabolism*; D011865:Radioisotope Dilution Technique
D000085:Acetates; D002250:Carbon Radioisotopes; D009097:Multienzyme Complexes; D000105:Acetyl Coenzyme A; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase