Manganese is a component of Galβ1,3-glucuronosyltransferase (GlcAT-I), which catalyzes the transfer of a glucuronic acid residue onto the nonreducing end of the second galactose of the proteoglycan (PG) trisaccharide primer Gal-β1,3-gal-β1,4Xyl-β1-O-Ser (Ouzzine et al., 2000).