OXIDATIVE DECARBOXYLATION OF GLYOXYLATE ION BY A DEPROTONATED-AMINE COPPER(III)-PEPTIDE COMPLEX

In basic solution copper(III) pentaglycine forms a species, Cu(H-4G5)2-which has three deprotonated-peptide groups and one deprotonated-amine group coordinated. Acting as a nucleophile, the deprotonated amine attacks glyoxylate ion followed by rapid electron-transfer and decarboxylation steps. The reaction stoichiometry is [FORMULA OMMITED] where half of the pentaglycine is converted to the N-formyl derivative (N-fG5). The reaction is first order in the deprotonated-amine species and first order in glyoxylate ion with a rate constant of 1.1X106 M-1 s-1 for the dehydrated form of glyoxylate ion. The rate is pH dependent, with a maximum about pH 13. The rate decreases at higher pH due to the formation of the unreactive glyoxylate dianion. Pyruvate and phenylglyoxylate also react with CuIII(H-4G5)2- and the relative reactivity is glyoxylate ⨠ pyruvate ⨠ phenylglyoxylate. © 1979, American Chemical Society. All rights reserved.