A pyruvate-containing peptide of proline reductase in Clostridium sticklandii.

Proline reductase in Clostridium sticklandii is composed of 10 apparently identical subunits. Each subunit contains a pyruvate residue that became labeled when the cell culture was supplemented with [14C]serine. No NH2-terminal amino acid was detected either by dansylation, by Edman degradation, or by aminopeptidase M digestion. The results suggest that the NH2 terminus may be blocked by pyruvate. A pyruvate-containing peptide, also blocked at the NH2 terminus, was isolated from the NH2-terminal portion of proline reductase. From amino acid analysis the peptide was found to be rich in basic amino acids and to have a molecular weight of 4621. Its COOH-terminal amino acid was found to be serine and since the peptide was released from proline reductase by very mild alkali hydrolysis, it is suspected that an ester bond is involved.