A novel catalysis by porcine pepsin in debranching guar galactomannan.

Abstract Background Pepsin (porcine stomach mucosa, E.C. 3.4.23.1), an acid protease catalyzes the hydrolysis (debranching) of guar galactomannan (GG), a co-polymer of mannose and galactose residues thereby showing its non-specific catalysis towards glycosidic substrates. Results and conclusions Use of non-specific inhibitors, chemical modification agents and peptide mapping of native and GG – bound pepsin upon proteolytic digestion with Staphylococcus aureus V8 protease revealed the involvement of Asp 138 residue in the catalysis, which was confirmed by computational modelling studies. General significance Here we show a novel mode of catalysis (other than proteolysis) by porcine pepsin with a different active site residue.