Oxoacids anion formation

The addition of an enolate anion to C02 to form a (3-oxoacid represents one of the commonest means of incorporation of C02 into organic compounds. The reverse reaction of decarboxylation is a major mechanism of biochemical formation of C02. The equilibrium constants usually favor decarboxylation but the cleavage of ATP can be coupled to drive carboxylation when it is needed, e.g., in photosynthesis. 

Decarboxylation of p-oxoacids. Beta-oxoacids such as oxaloacetic acid and acetoacetic acid are unstable, their decarboxylation being catalyzed by amines, metal ions, and other substances. Catalysis by amines depends upon Schiff base formation,232 while metal ions form chelates in which the metal assists in electron withdrawal to form an enolate anion.233 235... 

Constructing a substitutive name generally involves the replacement of hydrogen atoms in a parent structure with other atoms or atom groups. Related operations, often considered to be part of substitutive nomenclature, are skeletal replacement (Section IR-6.2.4.1) and functional replacement in oxoacid parents (Section IR-8.6). Note that some operations in parent hydride-based nomenclature are not substitutive operations (e.g. formation of cations and anions by addition of H+ and H, respectively, cf. Sections IR-6.4.1 and IR-6.4.5). Names formed by the modifications of parent hydride names described in those sections are still considered part of substitutive nomenclature. 

Pyruvate-dependent aldolases reversibly catalyze the aldol addition of p)u uvate or analogues to aldehydes yielding y-hydroxy-a-oxoacids (Figure 10.1). They exist as Class I aldolases (i.e., Schiff base/enamine formation) and Class 11 (i.e., metal cofactor and enolate formation) aldolases (Figure 10.2) [45, 46]. Class 11 pyruvate aldolases contain a Mg, Mn, or Co divalent metal cation in octahedral coordination, which stabilizes the nucleophile (i.e., p5U uvate anion) in the active site [45,47]. 

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