On the structure of the prosthetic group of citrate (pro-3S)-lyase.

The prosthetic group of citrate (pro-3S)-lyase from Klebsiella aerogenes as well as Streptococcus diacetilactis was obtained eigher by beta elimination or pronase digestion of the enzyme and purified by DEAE-cellulose chromatography. The compound was shown to contain 3 mol of PO4, 2 mol of ribose, and 1 mol of sulfhydryl/mol of adenine. 5'-AMP and dephospho-CoA are components of the prosthetic group. The evidence obtained so far support our proposed structure of 3' (or 2') leads to 1''-(5''-phosphoribosyl)dephospho-CoA for the prosthetic group of citrate lyase. The presence of one phosphomonoester group in the compound isolated after beta elimination and the absence of the same in the compound isolated after pronase digestion indicated that the prosthetic group is attached to the enzyme through a phosphodiester bond. Analyses of the pyruvate released by beta elimination and subsequent acid hydrolysis of the peptide-bound prosthetic group and its degradation products showed that the phosphodiester linkage is between the hydroxyl group of a serine residue of the protein and the 5''-PO4 group of the second ribose.