Purification of β-glucuronidase and structural assessment of the carbohydrate chains by lectin affinity immunoelectrophoresis

Abstract

The purification of rat liver β-glucuronidase from a lysosomal fraction by methods including affinity chromatography, chromatofocusing and preparative PAGE steps is described. Molecular weights of 300 000 and 150 000 were estimated by two dimensional gradient PAGE/immunoelectrophoresis of the lysosomal extract. Isoelectrofocusing in agarose gel followed by immunoelectrophoresis in the second dimension revealed the presence of at least five maxima in the range pH 4.3–7.4.

The structural assessment of the carbohydrate chains of lysosomal and microsomal β-glucuronidase was performed by lectin affinity immunoelectrophoresis. Reaction with Concanavalin A indicated the presence of bi-antennary complex, oligomannosidic and hybrid type structures, whereas the absence of tri- and tetra-antennary complex type structures was deduced from the lack of interaction with phytohemagglutinin-L. The reaction withLens culinaris agglutinin, Pisum sativum agglutinin andLotus tetragonolobus lectin revealed that part of the glycans contained a fucose α(1-6)-linked to theN-acetylglucosamine attached to asparagine. The presence of terminal β(1-4)-galactose residues was detected withRicinus communis agglutinin I.