Mass spectrometric identification of human phosphate cytidylyltransferase 1 as a novel calcium oxalate crystal growth inhibitor purified from human renal stone matrix

摘要

Background: A relatively small number of well-characterized inhibitors of kidney stone formation have beenidentified from the previous research involved in its formation. In this study conventional biochemicalmethods have been combined with recent advances in mass spectrometry (MS) to identify a novel calciumoxalate (CaOx) crystal growth inhibitor in human renal stone matrix.Methods: Proteins were isolated from the matrix of human CaOx containing kidney stones. Proteins havingMW> 10 kDa were subjected to anion exchange and molecular-sieve chromatography. Protein fractions weretested for their effects on CaOx crystal growth. Most potent fraction P2' was excised, in-gel tryptic digestedand identified by matrix assisted laser desorption/ionization-time of flight (MALD1-TOF) MS.Results: An anionic protein (MW-42 kDa) with potent inhibitory activity against CaOx crystal growth was purified.Its homogeneity was confirmed by RP-HPLC It was identified by MALDI-TOF-MS followed by database search onMASCOT server as human phosphate cytidylyltransferase 1, beta. Molecular weight of this novel CaOx crystal growthinhibitor from human renal stone matrix is also the same as that of human phosphate cytidylyltransferase 1, choline,beta.Conclusions: Human phosphate cytidylyltransferase 1, choline, beta is a novel CaOx crystal growth inhibitor. It isinvolved in the biosynthesis of phosphatidylcholine which happens to be an important constituent of humanrenal stones and is also reported to have an antilithiatic effect.