Lysate preparation from 50–200 mg of biopsy tissues for epimerase and O-sulfotransferase assays was performed as described (16). Protein concentration was estimated by the Bradford assay (Bio-Rad). The first step of the epimerization reaction is the abstraction of the C5-hydrogen from the chondroitin substrate, which will subsequently form water in the reaction buffer. Epimerase assay measures the presence of 3H2O derived from in vivo labeled 3H-C5 chondroitin substrate, and was performed as described previously (4).
