Analysis of the subunits, isoforms and substrate specificity of mouse liver alpha-L-fucosidase

1. SDS-PAGE indicates the presence of two major protein bands (57 and 62 kDa) for mouse fucosidase and Western blotting indicates that both bands are immunoreactive with polyclonal antibodies (PAbs) and/or monoclonal antibodies (MAbs) raised against human liver fucosidase. The lectins SNA and GNA recognized both mouse protein bands, indicating that both subunits are glycosylated and contain sialic acid residues. 2. Polyacrylamide gel-isoelectric focusing (PAG-IEF) indicated that mouse liver fucosidase contains at least seven isoforms, with three isoforms above pI 6.0, which were not detected in human liver fucosidase. Blotting indicates that the PAbs recognized seven mouse fucosidase isoforms (pIs 3.6-6.8) whereas the four MAbs did not appear to recognize any of the mouse isoforms. 3. The subunit composition of the separated isoforms of mouse alpha-L-fucosidase was investigated by SDS-PAGE. One-to-two closely-spaced protein bands are found in each isoform with a trend of increasing relative amounts of the high-M(r) band in the more acidic isoforms relative to the more neutral isoforms. 4. Human and mouse liver alpha-L-fucosidases hydrolyze L-Fuc from oligosaccharides and glycolipids at comparable rates, with the exception of ganglioside Fuc-GMI which was hydrolyzed by human, but not by mouse, alpha-L-fucosidase.