Purification and partial amino acid sequence of the cyanogen bromide fragments of muconolactone isomerase from Pseudomonas putida.

Muconolactone isomerase is shown to be resistant to proteolytic cleavage by trypsin. Cyanogen bromide cleavage at the methionine residues of the polypeptide is at least 95% complete. Six cyanogen bromide fragments are separated on DEAE-cellulose. One fragment is shown by amino acid analysis and carboxyl-terminal analysis to be an incomplete cleavage product. The five remaining fragments represent the entire polypeptide and have been ordered with respect to the entire muconolactone isomerase sequence. Approximately 50% of the polypeptide sequence could be determined from these fragments by the dansyl-Edman technique. The possible evolutionarily homologous origins of muconolactone isomerase and two analogous isomerases, carboxymuconolactone decarboxylase and sigma5-3-ketosteroid isomerase, are discussed.