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Elevated alkaline phosphatase occurs when levels of alkaline phosphatase (ALP) exceed the reference range. This group of enzymes has a low substrate specificity and catalyzes the hydrolysis of phosphate esters in a basic environment. The major function of alkaline phosphatase is transporting chemicals across cell membranes. [1]
The enzyme alkaline phosphatase (ALP, alkaline phenyl phosphatase, also abbreviated PhoA) is a phosphatase with 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 contrast, low levels of ALP is found in hypothyroidism, pernicious anemia, zinc deficiency, and hypophosphatasia. [6] ALP activity is significantly increased in the third trimester of pregnancy. [11] This is due to increased synthesis from the placenta as well as increased synthesis in the liver induced by large amounts of estrogens.
The discovery of dephosphorylation came from a series of experiments examining the enzyme phosphorylase isolated from rabbit skeletal muscle. In 1955, Edwin Krebs and Edmond Fischer used radiolabeled ATP to determine that phosphate is added to the serine residue of phosphorylase to convert it from its b to a form via phosphorylation. [ 3 ]
The enzyme is a monomer, the isoenzymes are due to the differences in the carbohydrate content (sialic acid residues). The most important ALP isoenzymes are α 1-ALP, α 2-heat labile ALP, α 2-heat stable ALP, pre-β ALP and γ-ALP. Increase in α 2-heat labile ALP suggests hepatitis whereas pre-β ALP indicates bone diseases.
The general reaction catalyzed by a phosphatase enzyme. Phosphatases catalyze the hydrolysis of a phosphomonoester, removing a phosphate moiety from the substrate. Water is split in the reaction, with the -OH group attaching to the phosphate ion, and the H+ protonating the hydroxyl group of the other product.
The decrease in ALP activity leads to an increase in pyridoxal 5’-phosphate (PLP), which is the major form of Vitamin B6, in the blood, although tissue levels of Vitamin B6 may be unremarkable [30] and correlates with disease severity. [31] Urinary inorganic pyrophosphate (PPi) levels are elevated in most hypophosphatasia patients and ...
Alkaline phosphatase, placental type is a membrane-bound glycosylated dimeric enzyme, also referred to as the heat-stable form, that is expressed primarily in the placenta, although it is closely related to the intestinal form of the enzyme as well as to the placental-like form.