Some characteristics of ?(1)-pyrroline-5-carboxylate dehydrogenase in rat cerebellum

?(1)-Pyrroline-5-carboxylate dehydrogenase (P5CDH) in rat cerebellum was assayed with a simple spectrophotometric method using high-speed supernatants of whole tissue homogenates. Kinetic analysis showed that the enzyme has K(m) values of 0.83 +/- 0.21 mM for ?(1)-pyrroline-5-carboxylate and 0.47 +/- 0.02 mM for NAD(+). Various cations inhibited P5CDH but only at relatively high concentrations. Several amino acids were strongly inhibitory in the order GABA > glycine > hydroxyproline > cysteine ? proline > glutamine > glutamate > alanine .