The fate of the carboxyl oxygens during D-proline reduction by clostridial proline reductase

D-Proline is converted to 5-amino valeric acid by D-proline reductase. This conversion involves the reductive cleavage of the α-carbon-nitrogen bond. We have examined the fate of the carboxyl oxygen atoms during conversion of D-proline to δ-NH2-valeric acid. 18O atoms from the carboxyl group of D-proline are not lost during conversion to product. In contrast, in the conversion of glycine to acetyl phosphate by glycine reductase a carboxyl oxygen atom is lost to solvent. An intermediate acyl-enzyme is found during the reduction of glycine. We conclude that the reduction of proline proceeds without the formation of an acyl enzyme intermediate.