Carnosine–anserine synthetase of muscle. 4. Partial purification of the enzyme and further studies of β-alanyl peptide synthesis

Abstract

The enzyme which promotes the synthesis of carnosine and anserine from their component amino acids has been purified about 100-fold, from an extract of chick pectoral muscle. The successive steps were fractionation with ethanol, followed by acetone, and then adsorption and selective elution of the enzyme from calcium phosphate gel. The purification experiments were severely hampered by the lability of the enzyme. Peptide-bond formation specifically required adenosine triphosphate, and magnesium ions could be replaced to a considerable extent by manganous ions. Carnosine synthesis was not readily reversible. Pyrophosphate was strongly inhibitory, and orthophosphate less so. Although the enzyme preparation promoted [P32] pyrophosphate incorporation into adenosine triphosphate, a dependency upon [beta]-alanine could not be clearly demonstrated. In fact, this process was suppressed by a high [beta]-alanine concentration. Fluoride ions inhibited both carnosine synthesis and pyrophosphate-adenosine triphosphate exchange. Attempts to detect an activated intermediate stage in carnosine synthesis were not successful. [beta]-Alanyl transfer from carnosine to 1-methyl-histidine to yield anserine proceeded very slowly, as compared with direct dipeptide synthesis by the enzyme.