Purification and Properties of an L-Arabinose Isomerase from Escherichia coli

Abstract

Abstract An l-arabinose isomerase has been purified 12-fold from l-arabinose-induced cultures of Escherichia coli B/r strain F' araB-24/araB-24. The enzyme is homogeneous in the ultracentrifuge and better than 98% pure by disc acrylamide electrophoresis. The s020,w is 12.65 x 10-13 sec at pH 7.6, 12.72 x 10-13 sec at pH 6.0, and 12.66 x 10-13 sec at pH 5.0. There is no evidence of concentration-dependent dissociation of the enzyme from pH 5.0 to pH 7.6. The molecular weight determined by sedimentation equilibrium is 3.62 ± 0.16 x 105. The enzyme exhibits only slight activity toward d-fucose, l-fucose, and d-xylose and no activity toward any of the other compounds tested. Several polyalcohols, from 3 to 5 carbon atoms in length, are effective inhibitors of the enzyme, and at least two of these, l-arabitol and ribitol, are competitive inhibitors. Activation by Mn++ has been demonstrated by means of enzyme dialyzed against ethylenediaminetetraacetic acid, but not with nondialyzed enzyme. An amino acid analysis is presented.