Isoforms of Amylase
Definition
The human genome encodes multiple AMY loci. AMY1 products are expressed in saliva; AMY2 products are expressed in the pancreas. The two sets of isoforms are closely related but have different profiles on electrophoresis and behave differently with antibody-based assays.
- Gene loci
- AMY1, AMY2
- AMY1 source
- Saliva
- AMY2 source
- Pancreas
- Differ in
- Electrophoretic mobility, antibody reactivity
Common questions
Why does the AMY1/AMY2 distinction matter for saliva identification?+
Amylase is present in several body fluids, so confirming that a stain contains the salivary AMY1 isoform rather than the pancreatic AMY2 isoform helps rule out contamination or a non-saliva source before an examiner relies on amylase activity as presumptive evidence of saliva.
Does a positive amylase test alone confirm saliva?+
No. Amylase activity is only presumptive because AMY1 also occurs at lower levels in other fluids. Isoform-specific methods, such as antibody-based assays like RSID-Saliva, are used to add specificity beyond a general amylase activity test.
Related terms
- Alpha-Amylase (Salivary)
- An enzyme encoded by the AMY1 gene and secreted by the parotid, submandibular, and sublingual glands. It cleaves starch at alpha-1,4-glycosidic bonds...
- Double-Swab Technique
- A collection method for dried biological stains in which a moistened swab rehydrates and lifts the stain from the surface, followed immediately...
- Phadebas Test
- A colorimetric presumptive test for alpha-amylase activity. Phadebas tablets contain a blue-dyed insoluble starch; amylase releases soluble blue dye that is measured...
- Presumptive vs Confirmatory Testing
- Presumptive tests (Phadebas) give rapid screening results but have cross-reactants; they justify further analysis. Confirmatory or highly specific tests (RSID-Saliva, mRNA analysis)...
- RSID-Saliva
- Rapid Stain Identification of Saliva. An immunochromatographic lateral-flow assay using monoclonal antibodies specific to human salivary amylase. More specific than Phadebas, with...