Another important enzyme to the efficient digestion of food eaten is protease. It is responsible for the primary breakdown of proteins and polypeptides from animals and plants and for proline dipeptides from gluten and casein. Proteases are released by the pancreas into the proximal small intestine, where they mix with proteins already denatured by gastric secretions and break them down into amino acids, the building blocks of protein, which will eventually be absorbed and used throughout the body.
While amylase and protease do a great job of breaking down carbohydrates and proteins, the body needs another enzyme for the breakdown of fats, oils, and triglycerides. This is where lipase functions. Lipase is necessary for the full digestion of fats to their smaller fatty acid components. At times, food may not be digested fully as it passes through the digestive tract.
A number of reasons may be at the root of this circumstance. This can result in the inefficient liberation of the nutrients in food. While this can be difficult to feel on a day to day basis, there are several things which can point to the need for a bit more focused digestive enzyme support.
Bacteria present in that area will ferment the maldigested macronutrients with the resulting byproducts being gases released to the digestive tract. This excessive gas buildup is what many people notice and initially report to their healthcare practitioner. Digestive enzymes including amylase, protease, and lipase represent a foundational aspect of gastrointestinal health.
Digestion starts with the sight, thought, or smell of food. When the brain anticipates an incoming meal, the vagus nerve sends a message to the stomach causing the release of acetylcholine. A 30 base pair insulin responsive element was identified in the mouse Amy gene The fact that mice express more than one functional Amy2 gene explains why total pancreatic amylase does not fall as much in diabetes as it does in rats Figure 1: Immunoflourescent localization of amylase in mouse pancreas green.
Nuclei are stained blue with DAPI. Patients with isolated amylase deficiency have been reported with carbohydrate malabsorption and its resulting symptoms 37, The patients evaluated have intact mRNA but no amylase protein.
This is similar to physiological pancreatic amylase deficiency at birth where lack of symptoms is in part due to low dietary starch requiring amylase and in part the action of salivary amylase. Amylase deficiency may be underreported due to mild symptoms. Recently, the amount of pancreatic amylase mRNA and amylase activity in the jejunum of carbohydrate sensitive rats was shown to be related to dietary glucose oxidation and visceral fat accumulation 5.
Determination of serum amylase has long been a mainstay in the diagnosis of acute pancreatitis 1, Serum amylase in normal individuals is about half salivary and half pancreatic form and each exists in several isoforms all of which contribute to total amylase.
Because of the existence of different assays and standards, the cutoff for acute pancreatitis is usually expressed related to the range of normal for the particular clinical laboratory. Levels greater than three times the upper limit of normal ULN are usually taken as indicative of pancreatitis.
A higher specificity is obtained when a higher cutoff point is used such as 5 or even 9 times the ULN, but at the cost of lower sensitivity. Utilizing assays to inhibit salivary amylase with wheat germ inhibitor or monoclonal antibodies 59 or removing it with immobilized monoclonal antibody 40 increase specificity somewhat and helps eliminate a contribution from tumors or other organs which primarily produce salivary amylase, but these tests are not always available.
The combination of serum lipase with amylase is generally available and helps when serum amylase levels have already peaked and declined. Amylase is also elevated in a variety of surgical, traumatic and neoplastic diseases 13, 46, Renal disease can reduce amylase filtration and enhance plasma levels, but this increase is usually small as glomerular filtration is only a small portion of amylase clearance Advanced imaging techniques may uncover a pancreatic abnormality in some of these patients.
It is also important to be aware that pancreatitis can occur without increased serum amylase especially with alcoholic pancreatitis or recurrent chronic pancreatitis In some of these cases, lipase is elevated. Thus, while amylase is still one of the most useful tests in diagnosing acute pancreatitis, it should be carried out in conjunction with other tests 1 along with an understanding of amylase metabolism.
Measurement of amylase secretion has become widely adopted to measure regulated protein secretion by pancreas or parotid fragments, slices or isolated acini. Amylase has filled this role because it is easy to measure, sensitive, and does not require activation as do proteases.
While for measurement of serum amylase in pancreatitis an absolute amount is desirable, most secretory measurements involve separately assaying the secretory product, usually in the incubation medium, and the tissue content and calculating the percent content released in a specified time.
While earliest measurements assayed the reducing groups produced in the hydrolytic product, most often with dinitrosalicylic acid, studies over the last 50 years have more commonly used the solubilized products of substrate or a colored or flourescent enzymatic product produced in a coupled reaction. Examples of this approach are Remazolbrilliant blue starch 48 , Procion Yellow labeled starch 27 , amylopectin anthranilate 43 , and Cibachronblue F3GA-amylose A common commercially available substrate is the Phadebas reagent in which an unspecified blue dye is linked to starch Most commonly these secretion studies are endpoint assays where tissue is incubated for a standard time and then aliquots of the medium are incubated with the starch substrate for a set time, centrifuged, and the product read in a spectrophotometer or flourometer 39, Some of these assays have been adapted to continuous readout with a flow through system 14, A second approach uses soluble colorless substrates that can be incubated in a plate reader with samples of the medium and lead to a colored or fluorescent product either directly or through a coupled reaction.
One primary substrate is ethylidene-paranitrophenol-G7. This can be read directly or the glucose released determined by glucose oxidase This type of assay has also been adapted to autoanalyzer technique.
Recently both types of assays have been used to determine human duodenal amylase with high correlation Amylase inhibitors particularly Acarbose, a pseudotetrasacharide, have been used it the treatment of type 2 diabetes where they have moderate effects to reduce peak postprandial glucose and Hemoglobin A1c. Normally, they are used as a second line medication often in conjunction with metformin Evidence also exists that Acarbose can reduce dumping syndrome after bariatric surgery A host of natural plant products with amylase inhibitor activities have been proposed or studied as a treatment for diabetes but little conclusive evidence exists for their effectiveness.
Amylase antibodies are widely available but not always well tested. The most commonly used is from Sigma-Aldrich cat A and is raised in rabbits injected with purified human salivary amylase. It is highly specific, reacts with both salivary and pancreatic amylase and in our hands works well for Western Blotting, immunofluorescence Fig.
A number of companies sell anti-amylase antibodies raised in sheep, rat or mice monoclonal that would allow double labeling with other rabbit antibodies. The most used amylase substrate for assays in research laboratories is the Phadebas reagent which is starch coupled to a blue dye. It can be used to measure amylase in plasma or serum as well as that secreted by pancreatic and parotid cells where it can be diluted to reduce cost.
Skip to main content. Search form Search. Williams, JA. Pancreatic Function Amylase Localization, Regulation and Deficiency Pancreatic amylase is similar to other secretory proteins and is synthesized in the rough endoplasmic reticulum.
Recently, the amount of pancreatic amylase mRNA and amylase activity in the jejunum of carbohydrate sensitive rats was shown to be related to dietary glucose oxidation and visceral fat accumulation 5 Serum Amylase as a Measure of Pancreatic Function in Pancreatitis Determination of serum amylase has long been a mainstay in the diagnosis of acute pancreatitis 1, Amylase secretion as a measure of regulated pancreatic or parotid secretion Measurement of amylase secretion has become widely adopted to measure regulated protein secretion by pancreas or parotid fragments, slices or isolated acini.
Amylase Inhibitors in Clinical Medicine Amylase inhibitors particularly Acarbose, a pseudotetrasacharide, have been used it the treatment of type 2 diabetes where they have moderate effects to reduce peak postprandial glucose and Hemoglobin A1c.
Tools for the study of Amylase a. Antibodies Amylase antibodies are widely available but not always well tested. Assay kits and reagents The most used amylase substrate for assays in research laboratories is the Phadebas reagent which is starch coupled to a blue dye.
Evaluating tests for acute pancreatitis. Am J Gastroenterol , PMID: The mechanism of porcine pancreatic alpha-amylase. Kinetic evidence for two additional carbohydrate-binding sites. Eur J Biochem , Alpers DH. Digestion and Absorption of Carbohydrates and Proteins. Functional regulation of sugar assimilation by N-glycan-specific interaction of pancreatic alpha-amylase with glycoproteins of duodenal brush border membrane.
J Biol Chem , J Nutr Genetic determination of amylase synthesis in the mouse. Substrate mimicry in the active center of a mammalian alpha-amylase: structural analysis of an enzyme-inhibitor complex. Structure 4: , Brannon PM. Adaptation of the exocrine pancreas to diet. Annu Rev Nutr , The structure of human pancreatic alpha-amylase at 1.
Mechanical digestion includes: chewing in the mouth churning in the stomach Chemical digestion involves enzymes. Different enzymes Enzymes can break down nutrients into small, soluble molecules that can be absorbed. Where enzymes are produced Enzyme Substrate End-products Where produced Salivary amylase Starch Maltose Salivary glands Protease Protein Amino acids Stomach, pancreas Lipase Lipids fats and oils Fatty acids and glycerol Pancreas Pancreatic amylase Starch Maltose Pancreas Maltase Maltose Glucose Small intestine Where digestion happens Proteases catalyse the breakdown of proteins into amino acids in the stomach and small intestine Lipases catalyse the breakdown of fats and oils into fatty acids and glycerol in the small intestine Amylase catalyses the breakdown of starch into maltose in the mouth and small intestine Maltase catalyses the breakdown of maltose into glucose in the small intestine.
Salivary amylase. Salivary glands. Amino acids.
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