Oxidation of L-thiazolidine-4-carboxylate by delta1-pyrroline-5-carboxylate reductase in Escherichia coli.

L-Thiazolidine-4-carboxylate (T4C, thiaproline) is a sulfur-containing proline analog that stimulates the immune system in aging mice and inhibits urinary tract pathogens such as Escherichia coli. A constitutive NADP+-dependent T4C dehydrogenase activity was detected in the soluble fraction of a putA::Tn5 mutant of E. coli lacking l-proline dehydrogenase and partially purified by ammonium sulfate precipitation, dye-affinity chromatography on Cibacron Blue 3GA agarose, and ion-exchange chromatography on DEAE-cellulose.