241 human active and 13 inactive phosphatases in total;
194 phosphatases have substrate data;
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336 protein substrates;
83 non-protein substrates;
1215 dephosphorylation interactions;
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299 KEGG pathways;
876 Reactome pathways;
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last scientific update: 11 Mar, 2019
last maintenance update: 01 Sep, 2023
In the de novo synthesis of phosphatidic acid (PA), lysophosphatidic acid (LPA) is initially formed by the esterification of sn-1 by glycerol 3-phosphate acyltransferase (GPAT) from glycerol 3-phosphate (G3P). Next, LPA is converted to PA by a LPA acyltransferase (AGPAT, also known as LPAAT). In addition to this, PA is also formed when phosphatidylcholine (PC) is hydrolyzed by phospholipases D1 and D2 (PLD1 and 2). PA is involved in acyl chain remodeling via cleavage by phospholipases followed by reacylation by acyltransferases (Ghomashchi et al. 2010, Singer et al. 2002, Prasad et al. 2011, Shindou & Shimizu 2009, Cao et al. 2006)
Glycosylphosphatidyl inositol (GPI) acts as a membrane anchor for many cell surface proteins. GPI is synthesized in the endoplasmic reticulum. In humans, a single pathway consisting of eleven reactions appears to be responsible for the synthesis of the major GPI species involved in membrane protein anchoring.
As a nascent protein fated to become GPI-anchored moves into the lumen of the endoplasmic reticulum, it is attacked by a transamidase complex that cleaves it near its carboxy terminus and attaches an acylated GPI moiety. The GPI moiety is deacylated, yielding a protein-GPI conjugate that can be efficiently transported to the Golgi apparatus
Dietary carbohydrates, fats, and proteins must be broken down to their constituent monosaccharides, fatty acids and sterols, and amino acids, respectively, before they can be absorbed in the intestine.Dietary lipids such as long-chain triacylglycerols and cholesterol esters are hydrolyzed in the stomach and small intestine to yield long-chain fatty acids, monoacylglycerols, glycerol and cholesterol through the action of a variety of lipases, and are then absorbed into enterocytes.Carbohydrates include starch (amylose and amylopectin) and disaccharides such as sucrose, lactose, maltose and, in small amounts, trehalose. The digestion of starch begins with the action of amylase enzymes secreted in the saliva and small intestine, which convert it to maltotriose, maltose, limit dextrins, and some glucose. Digestion of the limit dextrins and disaccharides, both dietary and starch-derived, to monosaccharides - glucose, galactose, and fructose - is accomplished by enzymes located on the luminal surfaces of enterocytes lining the microvilli of the small intestine.Dietary protein is hydrolyzed to dipeptides and amino acids by the action of pepsin in the stomach and an array of intestinal hydrolases. All of these enzymes are released in inactive (proenzyme) forms and activated by proteolytic cleavage within the gastrointestinal lumen (Van Beers et al. 1995; Yamada 2015)
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