title: Stability of D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid in relation to its possible occurrence as a degradation product of penicillin by the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61 and the membrane-bound dd-carboxypeptidase from Bacillus stearothermophilus.
abstract: The stability of D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid has been studied under various conditions. In 10 mM cacodylate, pH 6.5, and at 55 degrees C, D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid (at concentrations lower than 1 mM) is hydrolyzed into N-formyl-D-penicillamine with a half-life of 3 to 4 min. On this basis, it is very unlikely that D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid could be one of the end products resulting from the cleavage of benzylpenicillin by the DD-carboxypeptidase of Bacillus stearothermophilus (as reported by Hammarström and Strominger (1976) J. Biol. Chem. 251, 7947--7949). In 3 mM phosphate, pH 7.5, and at 37 degrees C, D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid (at concentrations lower than 1 mM) has a half-life of 45 min. On the basis of kinetic experiments carried out under these conditions with phenoxymethylpenicillin and the DD-carboxypeptidase-transpeptidase of Streptomyces R61, it is concluded that the primary product which arises from the thiazolidine moiety of the antibiotic molecule and gives rise to N-formyl-D-penicillamine, has a half-life of 10 min, a value which is not compatible with the hypothesis that D-5,5-dimethyl-delta2-thiazoline-4-carboxylic acid would be an intermediate involved in the fragmentation pathway.
mesh_terms: D000217:Acyltransferases / Q000378:metabolism*; D002268:Carboxypeptidases / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D002942:Circular Dichroism; D004355:Drug Stability; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D007700:Kinetics; D013058:Mass Spectrometry; D010406:Penicillins; D010458:Peptidyl Transferases / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013302:Streptomyces / Q000201:enzymology*; D013844:Thiazoles
chemical_list: D010406:Penicillins; D013844:Thiazoles; D000217:Acyltransferases; D010458:Peptidyl Transferases; D002268:Carboxypeptidases