Mechanism of formation of the carboxyl of acetate by acetogenic bacteria

Technical Report · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5763392

Ragsdale, S W

The final steps in acetyl-CoA synthesis are performed by carbon monoxide dehydrogenase (CODH), a nickel/iron-sulfur protein. Over the past three years, our goal has been to identify the steps leading to the formation of the carbonyl group of acetyl-CoA in Clostridium thermoaceticum. We have studied an EPR- detectible CODH-CO intermediate, called the Ni-Fe-C intermediate. CO, CO{sub 2}, and the carboxyl of pyruvate appear to enter the pathway via the Ni-Fe-C intermediate which serves as the precurser of the carbonyl of acetyl-CoA. Studies of the Ni-Fe-C species by Moessbauer, electron nuclear double resonance (ENDOR), and EPR spectroscopies and controlled potential coulometry, have suggested two possible structures for this center: a(4Fe-4S) center bonded to a nickel complex by a ligand bridge and a (Ni-3Fe-4S) center. The CO is proposed to be bound to either the Ni or Fe components of the complex. As described in detail below, we have studied each step shown and have made progress in elucidating the chemical structures and redox properties of the intermediates. It now seems likely that the Ni-Fe center which binds CO also is the site at which methyl-CODH and acetyl-CODH are formed. In a study of the structure and function of the other Fe-S centers in CODH, we have characterized a (4Fe-4S) cluster, a (Ni-Fe-C) center, and an iron-sulfur center with two oxidation reduction potentials which could be the precurser of the Ni-Fe-C species. In collaboration with Lars Ljungdahl (Univ. of Georgia), we have determined the complete amino acid sequence of CODH. We also have discovered that CODH can reduce nitrous oxide to nitrogen at significant rates. 25 refs., 8 figs.

• Research Organization: Wisconsin Univ., Milwaukee, WI (USA). Dept. of Chemistry
• Sponsoring Organization: DOE; USDOE, Washington, DC (USA)
• DOE Contract Number: FG02-88ER13875
• OSTI ID: 5763392
• Report Number(s): DOE/ER/13875-T2; ON: DE91012279
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ACETATES
BACTERIA
BIOLOGICAL PATHWAYS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CARBONYLATION
CARBOXYLIC ACID SALTS
CHALCOGENIDES
CHEMICAL REACTIONS
CLONING
CLOSTRIDIUM
DNA HYBRIDIZATION
DNA SEQUENCING
DNA-CLONING
DOCUMENT TYPES
ENZYME ACTIVITY
ENZYME INHIBITORS
ENZYMES
HYBRIDIZATION
METHYLATION
MICROORGANISMS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NITROUS OXIDE
OXIDES
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PROGRESS REPORT
REACTION INTERMEDIATES
REDOX REACTIONS
STRUCTURAL CHEMICAL ANALYSIS