- 100 units
Alpha amylase is an oligosaccharide endoglycosidase, an enzyme that cleaves an internal glycosidic bond within a poly or oligosaccharide. In the case of alpha amylase, it is the 1,4 linkage between two glucose moieties, cleaving the C-O bond between the C1 carbon and the oxygen, although which 1,4 linkage is cleaved is random1:
Alpha amylase requires calcium for activity, although complete activity only occurs in the presence of certain anions such as Cl-, Phosphate and others2. Although many tissues can produce alpha amylase3, the forms found in serum are most often from the pancreas and salivary glands2. Several isoenzymes have been detected and characterized from these tissue sources4,5,6. Alpha amylases can be found in a variety of body fluids and they are some of the few enzymes that can be found in urine from healthy individuals7. The main purpose in testing amylase, especially when the appropriate symptoms are present, is to diagnose pancreatitis and other primary and secondary pancreatic pathologies. This can be made more specific by testing for amylase isoenzymes specific to the pancreas6,8,9. However total amylase is still a very valuable diagnostic tool.
There is some evidence to suggest that lipase might be a superior indicator of pancreatitis6,10. In practice, both enzymes are often measured. Amylase may also play a role in diagnosing cancers other than pancreatic cancer, such as multiple myeloma and ovarian cancer, although it appears that at least in some of these cases the salivary form may be the more important form of amylase11,12,13.
Due to the non-specific nature of amylase, many substrates can be used and in the past this often resulted in considerable variability in measuring amylase, depending on which type of reagent was used. As a response, large substrates such as starch have been replaced with smaller, more consistent oligosaccharides2. Although no useful spectrophotometric changes occur during the amylase catalyzed hydrolysis of these glycosidic bonds, the release of glucose can be coupled to an enzyme such as hexokinase. This uses ATP to phosphorylate glucose to produce glucose-6-phosphate (G6P). This product can then be coupled to the enzyme glucose-6-phosphate dehydrogenase which uses NAD+ to oxidize G6P. The conversion of NAD+ to NADH can be monitored at 340 nm.
|ADULT REFERENCE RANGE2:||28-100 U/L|