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On the assumption that a rise in the pancreatic type isoamylases may not necessarily indicate underlying pancreatitis, genetic studies of human serum and urinary amylase isoenzymes have been performed with the use of electrophoresis. Although the preponderant increase in the two principal pancreatic isoamylases Amylase-1 and 2 has been accepted to be a specific index of pancreatic involvement, 1.68% of normal persons had Amylase-2 with an elevated amylase activity (named “Dominant Amylase-2”) up to the same levels as the major isoenzymes. Results of pancreozymin-secretin test and other laboratory findings of these persons with Dominant Amylase-2 were all within normal ranges. Pedigree studies confirmed an autosomal dominant mode of inheritance for this variant. The importance of serial determination and pedigree investigations has been shown to distinguish normal persons having Dominant Amylase-2 from patients with pancreatitis without elevated amylase activity. The existence of an inherited trait of pancreatitis-like isoamylase pattern in healthy individuals must be borne in mind before coming to a conclusion when amylase isoenzymes are used for clinical medicine, though preponderance of the pancreatic type isoenzymes in serum and urine has been revealed to be a characteristic finding in pancreatitis. Knowledge of amylase genetic polymorphism provides a scientific basis for amylase isoenzyme interpretation.

The nature of the postoperative hyperamylasemia in 27 patients undergoing open-heart surgery was investigated. An increase in serum amylase activity was found m 56% of the patients. Isoamylase analysis revealed that the rise was in the salivary-type isoamylase m all of these patients. Since the level of serum amylase activity was increased in the postoperative state with prolongation of extracorporeal circulation, it is conceivable that cellular hypoxia due to inadequate tissue perfusion may cause disturbances in cellular metabolism with a release of intracellular amylase. The finding of the salivary-type amylase in normal lung tissue, transient salivary-type hyperamylasemia in acute respiratory distress and increased amylase activity of the salivary-type in serum specimens from the left atrium compared to those from the right ventricle suggest that the origin of the amylase responsible for the transient postoperative hyperamylasemia in the salivary-type is due to the amylase released from lung tissues under hypoxia during and after operation.

Serum and urinary amylase isoenzymes were studied in an attempt to evaluate the usefulness of isoamylase analysis in the diagnosis of pancreatic diseases. The amylase in human serum and urine was separated into 4 to 5 distinct isoenzymes, which have mobilities consistent with those of the pancreatic isoamylases (Amylase-1, -2, -4 and -6) and the salivary isoamylases (Amylase-3, -5 and -7). The normal isoamylase pattern was Amylase-1, -2, -3 and -5. Amylase-4 and -6 could not be found in normal serum and urine. Amylase activity in Amylase-1 and/or -2 increased remarkably, having the normal isoamylase pattern, in the patients with elevated serum amylase activity after stimulation with pancreozymin-secretin or after endoscopie retrograde cholangiopancreatography. However, in the patients with acute pancreatitis, salivary type isoamylases disappeared and only the pancreatic type components were identified. It seems that the appearance of Amylase-4 and disappearance of the salivary components indicate severe pancreatic inflammation and that the apparent specificity of this isoenzyme pattern affords a mean for conforming the diagnosis of acute pancreatitis. However, the occurrence of an inherited trait in the pancreatic isoamylases of healthy individuals suggests that a rise in the pancreatic components may not necessarily indicate pancreatic disorders.

The mode of inhibition of a new complex oligosaccharide that inhibits the alpha-glucoside hydrolase activity of pancreatic and salivary alpha-amylase was studied. Kinetic analysis revealed a non-competitive type of inhibition with a Ki of 1.47 +/- 0.03 micrograms when tested against human pancreatic alpha-amylase and 3.89 +/- 0.08 micrograms against human salivary alpha-amylase. The inhibitory action of alpha-glucoside hydrolase inhibitor (alpha-GHI) on pancreatic amylase was observed over a wide range of pH (6.0--7.9), whereas the inhibition of salivary amylase was optimal at pH 6.5. Column chromatographic investigations suggested the possible formation of an enzyme-inhibitor complex because the mixture of alpha-GHI and pancreatic alpha-amylase was eluted as a single component through a Sephadex G200 column. However, this enzyme-inhibitor complex was easily separated into each component and the enzyme activity was fully recovered after electrophoresis.