Structure and function of amylases. I. The subunit structure of porcine pancreatic -amylase

The isozymes of porcine pancreatic α-amylase were reduced with dithiothreitol to two enzymatically active subunits which had molecular weights of 25,000 daltons each. These subunits could be isolated and separated from each other by chromatography on DEAE-cellulose. Subsequent treatment of the subunits with EDTA, DTT, and iodoacetamide gave derivatives that emerged in identical elution volumes from DEAE-cellulose columns and that migrated very rapidly and identically on disc-gel electrophoresis. These latter experiments suggested that the subunits might have similar primary structures. This hypothesis was tested by preparing tryptic peptide maps of the subunits. The results indicated that the subunits had very similar, if not identical, primary structures.