Enzyme-Catalyzed Condensation Reaction in a Mammalian α-Amylase. High-Resolution Structural Analysis of an Enzyme−Inhibitor Complex

• Published in: Biochemistry (Easton) 2001-06, Vol.40 (25), p.7700-7709
• Main Authors: Qian, Minxie, Nahoum, Virginie, Bonicel, Jacques, Bischoff, Hilmar, Henrissat, Bernard, Payan, Françoise
• Format: Article
• Language: English
• Subjects: Acarbose - metabolism; alpha-Amylases - antagonists & inhibitors; alpha-Amylases - chemistry; alpha-Amylases - metabolism; Amino Sugars - chemistry; Amino Sugars - metabolism; Animals; Anions; Binding Sites; Catalysis; Chlorides - metabolism; Cold Temperature; Computer Simulation; Disulfides - chemistry; Enzyme Inhibitors - chemistry; Enzyme Inhibitors - metabolism; Humans; Hydrolysis; Ligands; Models, Molecular; Pancreas - enzymology; Protein Conformation; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Swine
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi0102050

Mammalian α-amylases catalyze the hydrolysis of α-linked glucose polymers according to a complex processive mechanism. We have determined the X-ray structures of porcine pancreatic α-amylase complexes with the smallest molecule of the trestatin family (acarviosine-glucose) which inhibits porcine pancreatic α-amylase and yet is not hydrolyzed by the enzyme. A structure analysis at 1.38 Å resolution of this complex allowed for a clear identification of a genuine single hexasaccharide species composed of two α-1,4-linked original molecules bound to the active site of the enzyme. The structural results supported by mass spectrometry experiments provide evidence for an enzymatically catalyzed condensation reaction in the crystal.