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

摘要

The effect of various sulfur-containing amino acids on the activities of prolidase isoenzymes I and II isolated from erythrocytes of healthy individuals, and erythrocyte lysates from a patient with prolidase deficiency was investigated. The activity of prolidase I against glyc-ylproline was strongly enhanced by D-methionine. L-Methionine and D,L-methionine slightly enhanced the activity at low concentration, but N-acetyl-L-methionine had no effect. D-Ethionine, L-ethionine, and D,L-ethionine also enhanced the activity of prolidase I. D,L-Homocysteine enhanced the activity at low concentration, but inhibited the activity at 50 mM. The activity of prolidase II against methionylproline was enhanced by D-methionine, D,L-methionine, and L-methionine, but N-acetyl-L-methio-nine had no effect. D-Ethionine and D,L-ethionine strongly enhanced the activity of prolidase II compared with L-ethionine; D,L-homocysteine weakly enhanced the activity. D,L-Homocysteine-thiolactone inhibited the activities of prolidase I and II in a concentration-dependent manner. The effect of various sulfur-containing amino acids on prolidase activity against methionylproline in erythrocyte lysates from a patient with prolidase deficiency was almost the same as that on prolidase II. The kinetics of the activities of prolidase I, II, and patient prolidase were also studied. Their K_m values were changed by adding sulfur-containing amino acids, but V_(max) values were unchanged.