Alkaline Phosphatase

Alkaline phosphatase (ALP) is a plasma membrane-bound glycoprotein that plays a key role in the dephosphorylation (i.e., the hydrolysis of phosphate monoester) of various compounds at alkaline pH. Four ALP isoenzymes, each encoded by different gene loci, have been identified in humans. These include intestinal, placental, germ cell, and tissue nonspecific ALP (TNAP). TNAPs, which are ubiquitous, occur in three isoforms liver, bone, and kidney. Elevated ALP levels are commonly associated with cancer, bone diseases such as Paget's Disease, liver diseases such as hepatitis, blood disorders, and kidney diseases. Lowered levels of ALP, while less common, can indicate a zinc deficiency, malnutrition, and in some instances, a rare genetic disease known as hypophosphatasia, which affects teeth and bones.

Many biochemical and immunological methods have been used to selectively identify ALPs, including thermostability studies, immunologic methods, and differential inhibition studies with various amino acids and small peptides. Serum ALP tests can measure concentrations in adult tissue to deduce liver and bone disease. In biotechnology, ALP is typically conjugated to antibodies and used as a reporter enzyme in various immunoassays, such as ELISA, IHC/ICC/IF, western blotting.

References

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1. Sharma, U., Pal, D., & Prasad, R. (2014). Alkaline phosphatase: an overview. Indian journal of clinical biochemistry : IJCB, 29(3), 269–278. https://doi.org/10.1007/s12291-013-0408-y