Abstract
Some properties of crystalline extracellular pullulanase from Aerobacter aerogenes were compared with those of crystalline intracellular pullulanase. The amino acid compositions of those enzymes were found to be alike on the whole. Both enzymes also gave three different isoelectric points. The viscosity of the pullulan solution with pullulanase decreased rapidly at the early stage of the reaction. It was found that pullulanase cleaved at random α-1, 6-glucosidic linkages in pullulan. Ca2+ stimulated the activity of pullulanases (about 30%), while heavy metal ions except Mn2+ and Ag+ considerably inactivated the enzyme and particularly Hg2+ and Al3+ severely inactivated. Metal chelating agents and sulfhydryl reagents did not inhibit. N-Bromosuccinimide (NBS), above 2.5×10-5M, completely inhibited both pullulanases. It was suggested that tryptophan residues might possibly concern the enzymatic action of pullulanases.
