Article: Amylase

α-Amylase

Amylase (EC 3.2.1.1 ) (CAS# 9014-71-5) is a digestive enzyme classified as a saccharidase (an enzyme that cleaves polysaccharides). It is a constituent of human pancreatic juice and saliva, where it acts to breakdown long-chain carbohydrates (such as starch) into maltose which is then subsequently degraded by maltase, an enzyme, to glucose.

Amylase is also synthesized by many plants during the ripening of fruit and during the germination of cereal grains. Grain amylase is key to the production of malt. Many microbes also produce amylase to degrade extracellular starches.

Types

There are two isoforms of human amylase: pancreatic and salivary amylase. They behave differently on isoelectric focusing, and can also be separated in testing by using specific monoclonal antibodies.

Ptyalin

Ptyalin is the name given to the amylase found in saliva that breaks starch down into maltose and dextrin.

Substances acts upon ptyalin

Ptyalin act on starch breaking it down to soluble starch.(amylodextrin,erythrodextrin,achrodextrin and finally maltose). Ptyalin acts on alpha 1,4 glucosidic linkages,compound hydrolysis requires an enzyme which acts on branched products.

Optimum conditions for ptyalin

Optimum pH-5.6 - 6.9

Room temperatue- 37 degrees Celsius

Presence of certain anions and activators:

Chlorine and Bromine - most effective Iodine - less effective Sulfate and Phosphate - least effective

The Ptyalin Debate

For almost 200 years, medical science has understood that young infant saliva has very low levels of the amylase enzyme ptyalin. This has fuelled an on-going debate by numerous doctors including Chavasse, Sonsino, Tilden, Routh, Husley, Youmans, Dalton, Page, Shelton and Fry; to eliminate farinaceous (starchy) foods from the diet of infants, until full dentition [growing of teeth] which then co-incides with an infant's increased levels of ptyalin. ^[1]

Function

Alpha-amylase randomly cleaves the α(1-4)glycosidic linkages of amylose to yield dextrin, maltose or glucose molecules. It adopts a double displacement mechanism with retention of anomeric configuration.

Beta-amylase also catalyzes the hydrolysis of a-1,4 glycosidic bonds but only from the non-reducing end to yield maltose molecules. Beta-amylase is present in germinating seeds prior to germination whereas a-amylase and proteases appear once germination has begun.

Glucoamylase cleaves the α(1-4) and α(1-6)glycosidic linkages of amylose and amylopectin to yield glucose

Genetics

In humans, all amylase isoforms link to chromosome 1q21.

Detection

The test for amylase is easy to perform and has been the main test for pancreatitis. Labs will usually measure either pancreatic amylase, or total amylase. If only pancreatic amylase is measured, an increase will not be noted with mumps or other salivary gland trauma.

Unfortunately, because of the small amount present, timing is critical when sampling blood for this measurement. Blood should preferably be taken soon after a bout of pancreatitis pain, otherwise it is excreted rapidly by the kidneys.

Interpretation

Increased plasma levels in humans are found in:

• Salivary trauma (including anaesthetic intubation).
• Mumps — due to inflammation of the salivary glands.
• Pancreatitis — because of damage to the cells that produce amylase.
• Renal failure — due to reduced excretion.

Total amylase readings of over 10X the upper limit of normal (ULN) are suggestive of pancreatitis. 5-10x times the ULN may indicate ileus or duodenal disease or renal failure, and lower elevations are commonly found in salivary gland disease.