The use of liquid chromatography-mass spectrometry for the identification and quantification of urinary iminodipeptides in prolidase deficiency.
It has been reported that the urine of patients with prolidase deficiency contains various iminodipeptides with a carboxyl-terminal proline (hydroxyproline). These iminodipeptides have hitherto been detected indirectly by acid hydrolysis or enzymatic digestion, followed by amino acid analysis. In the present study, it was shown that X-Pro could be distinguished from Pro-X when the iminodipeptides were analysed directly by liquid chromatography coupled with atmospheric pressure ionization mass spectrometry (LC/API-MS), with scanning of the protonated molecule ions ([M+H]+). The same procedure also successfully quantified urinary iminodipeptides from patients with prolidase deficiency. A quantitative investigation of two siblings with prolidase deficiency revealed that the patient with severe clinical symptoms excreted more iminodipeptides than the other who did not have serious symptoms. LC/API-MS also revealed iminodipeptides (Gly-Hyp and Pro-Hyp) in the urine of the mother of the patients and in normal volunteers. Patients excreted much more Pro-Hyp than normal volunteers, whereas no quantitative differences were found between the mother and controls. In patients, the excretion of large quantities of X-Pro is due to their very low prolidase activity towards this type of substrate. In the erythrocytes of patients, prolidase activity towards X-Hyp was extremely low; even in the mother and normal volunteers, it was remarkably low in comparison with the activity against X-Pro.
Sugahara
K
K
Department of Chemistry, Kochi Medical School, Japan.
Ohno
T
T
Arata
J
J
Kodama
H
H
D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004150:Dipeptidases / Q000172:deficiency* / Q000652:urine; D004151:Dipeptides / Q000652:urine*; D005260:Female; D006801:Humans; D007098:Imino Acids / Q000652:urine*; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D004151:Dipeptides; D007098:Imino Acids; D004150:Dipeptidases; C022449:proline dipeptidase