Alkaline Phosphatase- Pathology

Alkaline phosphatase (ALP, ALKP, ALPase, Alk Phos) (EC or basic phosphatase is a homodimeric protein enzyme of 86 kilodaltons. Each monomer contains five cysteine residues, two zinc atoms, and one magnesium atom crucial to its catalytic function, and it is optimally active at alkaline pH environments. ALP has the physiological role of dephosphorylating compounds. The enzyme is found across a multitude of organisms, prokaryotes and eukaryotes alike, with the same general function but in different structural forms suitable to the environment they function in.

Alkaline phosphatase is found in the periplasmic space of E. coli bacteria. This enzyme is heat stable and has its maximum activity at high pH. In humans, it is found in many forms depending on its origin within the body – it plays an integral role in metabolism within the liver and development within the skeleton. Due to its widespread prevalence in these areas, its concentration in the bloodstream is used by diagnosticians as a biomarker in helping determine diagnoses such as hepatitis or osteomalacia. The level of alkaline phosphatase in the blood is checked through the ALP test, which is often part of routine blood tests.

The levels of this enzyme in the blood depend on factors such as age, gender, blood type. Blood levels of alkaline phosphatase also increase two to four times during pregnancy. This is a result of additional alkaline phosphatase produced by the placenta. Additionally, abnormal levels of alkaline phosphatase in the blood could indicate issues relating to the liver, gall bladder or bones. Kidney tumors, infections as well as malnutrition has also shown abnormal level of alkaline phosphatase in blood. Alkaline phosphatase levels in a cell can be measured through a process called "The scoring method". "The scoring method" is a technique used where a sample of the enzyme is extracted from the inside of different individual's blood cells and is analyzed and compared for different enzyme activity. A blood smear is usually taken and undergoes differential centrifugation to isolate Leukocytes and staining to categorize each leukocyte into specific “leukocyte alkaline phosphatase indices.” This marker is designed to distinguish leukocytes and determine different enzyme activity from each sample's extent of staining.

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