Characterization of prolidase activity in erythrocytes from a patient with prolidase deficiency: Comparison with prolidase I and II purified from normal human erythrocytes

Objectives: The purpose of this study was to investigate the effect of various amino acids and their metabolites on the activities of prolidase I and II from human erythrocytes compared to those in a patient with prolidase deficiency. Design and methods: Prolidase I and II from human erythrocytes were purified by using column chromatography. Prolidase activity against various iminodipeptides was determined by spectrophotometry using Chinardʹs method. Results: The activities of prolidase I and II against glycylproline and methionylproline were enhanced by glycine, l- and d-isoforms of alanine and serine and d-isoforms of valine, leucine and isoleucine. l-isoforms of branched amino acids inhibited the activity of prolidase I. On the other hand, the activity of prolidase II was enhanced by all of these l-branched amino acids. The patientʹs prolidase activity was also enhanced by all the l- and d-branched amino acids. Conclusion: The activities of prolidase I and II against various iminodipeptides were prominently enhanced by glycine, but the effect of l-valine differed between the two enzymes. Enzymatic properties of the patientʹs prolidase were essentially the same as those of prolidase II.