Partial purification and some properties of delta1-pyrroline-5-carboxylate reductase from Escherichia coli

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Abstract
.DELTA.1-Pyrroline-5-carboxylate (PCA) reductase [L-proline:NAD(P)+5-oxidoreductase, EC 1.5.1.2] was purified > 200-fold from Escherichia coli K-12. It has a MW of .apprx. 320,000. PCA reductase mediates the pyridine nucleotide-linked reduction of PCA to proline but not the reverse reaction even at high substrate concentrations. The partially purified preparation is free of competing pyridine nucleotide oxidase, PCA dehydrogenase and proline oxidase activities. The Km values for the substrate, PCA, with NADPH or NADH as cofactor are 0.15 and 0.14 mM, respectively. The Km values determined for NADPH and NADH are 0.03 and 0.23 mM, respectively. Although NADPH or NADH can function as cofactor, the activity observed with NADPH is greater. PCA reductase is not repressed by growth in the presence of proline, but it is inhibited by the reaction end products, proline and NADP.