|Protein Name||Alkaline phosphatase, tissue-nonspecific isozyme|
|Milk Fraction||Whey, MFGM, Exosome|
|Ref Sequence ID||NP_789828.2|
|Protein Existence Status||Reviewed: Experimental evidence at protein level|
|Protein Function||hydrolysis of phosphate monoesters at basic pH values; bone isoenzyme may be involved in mammalian bone calcification and the intestinal isoenzyme is thought to play a role in the transport of phosphate into epithelial cells of the intestine; alkaline phosphatase is an important serum analyte and its elevation in serum is correlated with the presence of bone,liver, and other diseases. Alkaline phosphatase (ALP) is a ubiquitous membrane-bound glycoprotein capable of providing inorganic phosphate by catalyzing the hydrolysis of organic phosphate esters, or removing inorganic pyrophosphate that inhibits calcification.|
|Biochemical Properties||highest activity was obtained in ethanolamine buffer (pH 8.2 to 10.49); In CAPS [3-(cyclohexylamino)-I-propanesulfonic acid[ buffer, activity was maximum between pH 10.5 and 11.1]; The maximum activity in diethanolamine buffer occurred from pH 10.1 to 10.7; The optimal pH for alkaline phosphatase activity is affected by a number of variables: the type of buffer, the specific substrate used, the concentration of the substrate, and the stability of the enzyme at high pH; Activation of alkaline phosphatase is observed with Co 2+, Mn2+, and Mg2+, whereas Zn ions are inhibitory. Calcium ions have little effect on activity; The highest activities were obtained at pH 10.1 with four substrates containing aromatic groups: a-naphthyl phosphate, pNPP, methylumbelliferyl phosphate, and phosphotyrosine. The alkaline phosphatase hydrolyzed 10 substrates with maximum activity at pH 9.0. ß Casein, which is a poor substrate, showed maximum hydrolysis at pH 8.1;Levamisole is a potent inhibitor of mammalian alkaline phosphatases found in liver, kidney and bone; Homoarginine inhibits the alkaline phosphatase from fat globule membranes, microsomes and liver to a much greater extent than the intestinal alkaline phosphatase|
|Significance in milk||covalently bound to bovine mammary microsomal membranes and milk fat globule membranes through linkage to phosphatidylinositol; has been found in the mammary gland of rat, cow, cat, rabbit, goat, mare, dog, sheep, and human; as detected in humans, AP decresed from colustrum to mature milk; ALP can dephosphorylate casein, phosphoprotein, under suitable conditions|
|PTMs||Disulfide bond formation,N-Linked Glycosylation at Asn, GPI-anchor formation, Lipoprotein formation, Phosphorylation at Ser|
| Site(s) of PTM(s) |
|Predicted Disorder Regions||NA|
|TM Helix Prediction||No TM helices|
|Significance of PTMs||N-glycosylation is absolutely essential for TNAP activity, but not for that of the placental or intestinal enzymes.Asn-213 is a possible N-glycosylation site, and it suggests that this sugar chain plays a key role in enzyme regulation.|
|Bibliography||1. Bingham, E. W. and Malin, E. L. (1992) ‘Alkaline phosphatase in the lactating bovine mammary gland and the milk fat globule membrane. Release by phosphatidylinositol-specific phospholipase C’, Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 102(2), pp. 213–218. doi: 10.1016/0305-0491(92)90113-6. |
2. Bingham, E. W., Garver, K. and Powlen, D. (1992) ‘Purification and properties of alkaline phosphatase in the lactating bovine mammary gland.’, Journal of dairy science, 75(12), pp. 3394–401. doi: 10.3168/jds.S0022-0302(92)78115-6.
3. Hamilton, T. A., Górnicki, S. Z. and Sussman, H. H. (1979) ‘Alkaline phosphates from human milk. Comparison with isoenzymes from placenta and liver’, Biochemical Journal, 177(1), pp. 197–201. doi: 10.1042/bj1770197. 4.Sato M, Saitoh I, Kiyokawa Y, Iwase Y, Kubota N, Ibano N, Noguchi H, Yamasaki Y, Inada E. Tissue-Nonspecific Alkaline Phosphatase, a Possible Mediator of Cell Maturation: Towards a New Paradigm. Cells. 2021 Nov 28;10(12):3338. doi: 10.3390/cells10123338. PMID: 34943845; PMCID: PMC8699127. 5.Nosjean O, Koyama I, Goseki M, Roux B, Komoda T. Human tissue non-specific alkaline phosphatases: sugar-moiety-induced enzymic and antigenic modulations and genetic aspects. Biochem J. 1997 Jan 15;321 ( Pt 2)(Pt 2):297-303. doi: 10.1042/bj3210297. PMID: 9020858; PMCID: PMC1218068.