Effect of pressure on the mechanism of hydrolysis of maltotetraose, maltopentaose, and maltohexose catalyzed by porcine pancreatic alpha-amylase.

Pressure effects on the time course of the products' composition accompanying the hydrolysis of maltooligosaccharides [maltotetraose (G4) maltopentaose (G5), and maltohexaose (G6)] catalyzed by porcine pancreatic alpha-amylase (PPA) were measured up to 300MPa at 30 degrees C. The composition of products, glucose (G ), maltose (G2), and maltotriose (G3), for the hydrolysis of G4, and G5 substrates changed a little by compression. But for G6 substrate, pressure induced some changes in the composition of products, G2, G3, and G4, respectively. From the pressure dependence of the observed rate constants on PPA catalyzed hydrolysis of G6, the volume difference between two kinds of Michaelis complexes of alpha-amylase-G6 is about 5.4 cm3/mol. The mechanism of an interesting pressure-induced reaction catalyzed by PPA is discussed in the terms of the reaction volumes.