Objectives: Patients with Ehlers-Danlos syndrome were described to contain reduced activities of beta4-galactosyltransferase-7 (beta4Gal-T7). Therefore, measurement of beta4Gal-T7 activity can help to characterize defects in proteoglycan biosynthesis in patients with connective tissue diseases.
Design and methods: We developed a sensitive and specific method to assay beta4Gal-T7 which is based on the transfer of galactose from UDP-galactose to the synthetic peptide Bio-BIK-F-Xyl.
Results: Calibration curves exhibited consistent linearity in the range of 10-2000 microg/L Bio-BIK-F-Xyl-Gal, corresponding to a beta4Gal-T7 activity of 3.5-659 microU/L. The limit of detection and the lower limit of quantification were 3.70 microg/L (1.22 microU/L) and 4.50 microg/L Bio-BIK-F-Xyl-Gal (1.48 microU/L beta4Gal-T7 activity), respectively. Interassay imprecision (CV) was 8.1-13.1% in the range from 15.9 to 659 microU/L, and mean recovery was 85.3% (range 61.7-106.3%).
Conclusions: This sensitive, robust and interference-free LC-MS/MS assay allows an accurate determination of beta4Gal-T7 activity in human body fluids.