Amylase

About: Amylase is a research topic. Over the lifetime, 14164 publications have been published within this topic receiving 296069 citations.

Effect of dietary change upon the amylase and trypsin activities of the rat pancreas.

Abstract: Most of the reports on enzyme adaptation, by ourselves and other workers, have been concerned with the enzymes of micro-organisms. We have, however, also made a few observations on rats, some of which have been concerned with digestive enzymes (e.g. Lawrie & Yudkin, 1949; Roberts & Yudkin, 1961). The work to be described was carried out as a confirmation and extension of that reported by Ivy and his colleagues (Grossman, Greengard & Ivy, 1942-3, 1944). These workers measured the activity of three pancreatic enzymes : amylase, trypsin and lipase. Our own work is concerned with the first two. Grossman et al. (1942-3) in their main experiment fed rats for 21 days on one of four purified diets, in which the chief differences were in the proportion of carbohydrate as starch, protein as casein and fat as lard. The control diet contained 47% starch, 18 % casein and 18 % fat. When the starch was increased to 67 % of the diet, there was a 40 yo increase in the amylase activity of the pancreas and a 50 yo fall in the trypsin activity. When the casein was increased to 67% of the diet, there was a 20% fall in amylase activity and a threefold increase in trypsin activity. When the lard was increased to 54 % of the diet, there was a 65 % fall in amylase activity and no change in trypsin activity. It should perhaps be added that the four diets differed in the proportion of all three major constituents, so that, for example, the high-carbohydrate diet contained 67 % starch, 15 % casein and 27 % lard. In later experiments, the same workers showed that a substitution of the starch in the control diet by glucose increased amylase activity by about 20%, but did not affect trypsin activity (Grossman et al. 1944). A substitution of the casein by hydrolysed casein decreased trypsin activity by about 20 %, but did not affect amylase activity. The daily injection of protamine zinc insulin into rats given the control diet resulted in a 30 % fall in amylase activity, but did not affect trypsin activity.

Hormonal stimulation in the exocrine pancreas results in coordinate and anticoordinate regulation of protein synthesis.

Abstract: 24-h intravenous caerulein infusion studies in the rat were combined with in vitro amino acid incorporation studies followed by high-resolution separation of proteins by two-dimensional isoelectric focusing and SDS gel electrophoresis to study the extent to which persistent changes in the biosynthesis of exocrine pancreatic proteins are regulated by cholecystokinin-like peptides. Beginning in the third hour of optimal hormone infusion at 0.25 microgram kg-1 h-1, changes were observed in the synthetic rates of 12 proteins, which progressed over the course of the 24-h study. Based on coordinate response patterns, exocrine proteins could be classified into four distinct groups. Group I (trypsinogen forms 1 and 2) showed progressive increases in synthetic rates reaching a combined 4.3-fold increase over control levels. Group II (amylase forms 1 and 2) showed progressive decreases in synthesis to levels 7.1- and 14.3-fold lower than control levels, respectively. Group III proteins (ribonuclease, chymotrypsinogen forms 1 and 2, procarboxypeptidase forms A and B, and proelastase 1) showed moderate increases in synthesis, 1.4-2.8-fold, and group IV proteins (trypsinogen 3, lipase, proelastase 2, and unidentified proteins 1-4) did not show changes in synthesis with hormone stimulation. Regulation of protein synthesis in response to caerulein infusion was specific for individual isoenzymic forms in the case of both trypsinogen and proelastase. The ratio of biosynthetic rates of trypsinogen forms 1 + 2 to amylase forms 1 + 2 increased from a control value of 0.56 to 24.4 after 24 h of hormonal stimulation (43.5-fold increase). Biosynthetic rates for an unidentified protein (P23) with an Mr = 23,000 and isoelectric point of 6.2 increased 14.2-fold, and the ratio of synthesis of P23 to amylase 2 increased 200-fold during caerulein infusion. During hormone stimulation the anticoordinate response in the synthesis of pancreatic glycosidases (decreased synthesis) and serine protease zymogens (increased synthesis) explain previous observations that showed little change in rates of total protein synthesis under similar conditions.