Crystal Structure of Pig Pancreatic α‐amylase Isoenzyme II, in Complex with the Carbohydrate Inhibitor Acarbose

Open Access
Publisher Website
Google Scholar
Abstract
Two different crystal forms of pig pancreatic α‐amylase isoenzyme II (PPAII), free and complexed to a carbohydrate inhibitor (acarbose), have been compared together and to previously reported structures of PPAI. A crystal form obtained at 4°C, containing nearly 72% solvent, made it possible to obtain a new complex with acarbose, different from a previous one obtained at 20°C [Qian, M., Buisson, G., Duée, E., Haser, H. & Payan, F. (1994) Biochemistry 33, 6284–6294]. In the present form, six contiguous subsites of the enzyme active site are occupied by the carbohydrate ligand; the structural data indicate that the binding site is capable of holding more than the five glucose units of the scheme proposed through kinetic studies. A monosaccharide ring bridging two protein molecules related by the crystal packing is located on the surface, at a distance of 2.0 nm from the reducing end of the inhibitor ligand; the symmetry‐related glucose ring in the crystal lattice is found 1.5 nm away from the non‐reducing end of the inhibitor ligand.