Measurement of iminodipeptides in the serum of patients with prolidase deficiency using liquid chromatography-mass spectrometry.

Iminodipeptides containing C-terminal proline or hydroxyproline were determined in sera from patients with prolidase deficiency, in their mother's serum, and in the sera of unrelated controls, using liquid chromatography-mass spectrometry with an atmospheric pressure ionization interface system. The separation was carried out on a reversed phase column using 1 g/l aqueous trifluoroacetic acid-methanol (75 + 25, by vol.). The quasi-molecular ions ([M + H])+ of various iminodipeptides containing C-terminal proline and hydroxyproline were observed in the sera of patients with prolidase deficiency, using selected ion monitoring. The quasi-molecular ions ([M + H])+ of iminodipeptides containing C-terminal proline were not observed in the sera of normal subjects or the patients' mother, but the latter did contain various iminodipeptides with C-terminal hydroxyproline. This method proved useful for the determination of iminodipeptides in the sera of patients with prolidase deficiency.