Characterization and function of pig intestinal sucrase-isomaltase and its separate subunits.

Papain-solubilized pig intestinal sucrase-isomaltase was purified to homogeneity in a four-step process with a yield of 50%. The substrate specificities of the two enzyme activities were studied together and separately after inactivation or inhibition of one of the activities. Michaelis constants, maximum velocities and time courses of hydrolysis of several substrates, in particular alpha-limit dextrins, were used to characterize this complex of alpha-glucosidases. The participation of the enzyme complex in the hydrolysis of alpha-limit dextrins and more generally in pathways for starch breakdown in the pig digestive tract is examined and discussed.