PON-1 carbamylation is enhanced in HDL of uremia patients

PON-1 carbamylation is enhanced in HDL of uremia patients

High-density lipoprotein (HDL) carbamylation has been known in uremia patients.Paraoxonase-1 (PON-1) is an important HDL protein responsible for HDL anti-oxidant,arylesterase and lactonase activities. PON-1 carbamylation in uremic HDL has neverbeen explored. We isolated HDL from uremia patients and control healthy subjects forstudy. Sandwich ELISA was used to estimate carbamylated PON-1 protein expression inHDL, and nanoflow liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS)was applied to identify the amino acid in PON-1 carbamylated. PON-1 enzyme activitieswere estimated by substrates conversion method. HDL anti-oxidant activity was gauged byfluorescence changes of indicator dye in the presence of H2O2. Our study results provedthat the degree of PON-1 carbamylation was higher in uremic HDL than in control HDL.Sandwich ELISA study showed that carbamylated PON-1 concentration in uremic HDL was1.49 ± 0.08 fold higher than that in HDL from controls (p < 0.05). The nanoLC-MS/MSshowed that the carbamylation of lysine 290 (K290) of PON-1, a residue adjacent to PON-1 activity determining site, was detected in uremic HDL but not detected in control HDL.K290 carbamylation leads to local conformation changes that reduce accessible solventaccessibility. The HDL paraoxonase, arylesterase, and lactonase activities were all significantlylower in uremia patients than in control subjects. Additionally, HDL antiantioxidantability was also lower in uremia patients. Carbamylation of PON-1 in uremiapatients could be one of the factors in impairing PON-1 enzyme activities and HDL antioxidationfunction.