Biochemistry - The Chemical Reactions of Living Cells, Volume 2 - D. Metzler 1980

Organization of Metabolism: Catabolic Pathways
Oxidation Pathways Associated with the Tricarboxylic Acid Cycle
Oxidation of oxalate to CO2 via formate

For some organisms, such as pseudomonads, formic acid serves as a complete energy source. Bacterial utilization of oxalate [equation (9-11)] proceeds via The formation of formate, as well as oxalyl- and formyl-CoA. Notably, one of the steps involves a Thiamine diphosphate-dependent $\alpha$-Cleavage; the energy of formyl-CoA is utilized via a CoA transferase (Chapter 7, Section E,4) to generate oxalyl-CoA [28].

The oxidation of formate to СО₂ is catalyzed by formate dehydrogenase, a NAD⁺-dependent enzyme containing selenium, molybdenum, and iron [29, 30]. In E. coli, this protein is membrane-bound and contains one atom each of selenium and molybdenum, along with a heme group and several iron-sulfur centers (Chapter 10, Section B). The protein molecule is composed of Three types of peptide chains. Apparently, 12 chains (four of each type) form an aggregate with a Molecular Weight of ~590,000 (see also Supplement 9-E). Animals and plants also possess The ability to oxidize formate [31]. However, in these organisms, free formate is not a typical metabolic intermediate. For instance, The breakdown of glyoxylate generally occurs via the Dicarboxylic Acid Cycle (Fig. 9-5) rather than through oxidative decarboxylation yielding formyl-CoA and formate. In most cases, formate and formaldehyde are incorporated into metabolic pathways while being covalently bound to tetrahydrofolic acid (Fig. 8-20).

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