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
Cell membrane Basolateral cell membrane Note=Detected in the erythrocytecell membrane and on the basolateral membrane of alpha-intercalated cells in the collecting duct in the kidney
Function (UniProt annotation)
Functions both as a transporter that mediateselectroneutral anion exchange across the cell membrane and as astructural protein Major integral membrane glycoprotein of theerythrocyte membrane; required for normal flexibility andstability of the erythrocyte membrane and for normal erythrocyteshape via the interactions of its cytoplasmic domain withcytoskeletal proteins, glycolytic enzymes, and hemoglobinFunctions as a transporter that mediates the 1:1 exchange ofinorganic anions across the erythrocyte membrane Mediateschloride-bicarbonate exchange in the kidney, and is required fornormal acidification of the urine
One of the important roles of the collecting duct segment of the kidney nephron is acid secretion. As daily food intake loads acid into the body, urinary acid excretion is essential, and urine pH can drop as low as 4.5. The alpha-intercalated cell of collecting duct is the main responsible for hydrogen secretion into the urine. The carbon dioxide, which is generated in the cells and enters from the blood, is changed to carbonic acid. This carbonic acid is divided into hydrogen ion and bicarbonate ion. Intracellular CA II catalyses the formation of these ions. The hydrogen ion is secreted into the lumen by the luminal H(+)-ATPase. The bicarbonate ion is transported to the blood side by the anion exchanger type 1. Hydrogen ion in the lumen is trapped by urinary buffers. These include ammonium and phosphate.
Carbon dioxide (CO2) in plasma is hydrated to yield protons (H+) and bicarbonate (HCO3-) by carbonic anhydrase IV (CA4) located on the apical plasma membranes of endothelial cells. Plasma CO2 is also taken up by erythrocytes via AQP1 and RhAG. Within erythrocytes CA1 and, predominantly, CA2 hydrate CO2 to HCO3- and protons (reviewed in Geers & Gros 2000, Jensen 2004, Boron 2010). The HCO3- is transferred out of the erythrocyte by the band 3 anion exchange protein (AE1, SLC4A1) which cotransports a chloride ion (Cl-) into the erythrocyte.Also within the erythrocyte, CO2 combines with the N-terminal alpha amino groups of HbA to form carbamates while protons bind histidine residues in HbA. The net result is the Bohr effect, a conformational change in HbA that reduces its affinity for O2 and hence assists the delivery of O2 to tissues
Erythrocytes circulating through the capillaries of the lung must exchange carbon dioxide (CO2) for oxygen (O2) during their short (0.5-1 sec.) transit time in pulmonary tissue (Reviewed in Jensen 2004, Esbaugh and Tufts 2006, Boron 2010). CO2 bound as carbamate to the N-terminus of hemoglobin and protons (H+) bound to histidine residues in hemoglobin are released as hemoglobin (HbA) binds O2. Bicarbonate (HCO3-) present in plasma is taken up by erythrocytes via the band3 anion exchanger (AE1, SLC4A1) and combined with H+ by carbonic anhydrases I and II (CA1/CA2) to yield water and CO2 (Reviewed by Esbaugh and Tufts 2006). CO2 is passively transported out of the erythrocyte by AQP1 and RhAG. HCO3- in plasma is also directly dehydrated by extracellular carbonic anhydrase IV (CA4) present on endothelial cells lining the capillaries in the lung
Respiratory oxidation in the mitochondria produces carbon dioxide (CO2) as a waste product. CO2 is in equilibrium with bicarbonate (HCO3-) and is the body's central pH buffering system. HCO3- is charged so cannot move across membranes unaided. The bicarbonate transport proteins move bicarbonate across the membrane. There are 14 genes which encode these transport proteins in mammals. Applying the Human Genome Organization's sytematic nomenclature to human genes, the bicarbonate transporters belong to the SLC4A and SLC26A families. Within SLC4A, there are two distinct subfamilies, functionally corresponding to the electroneutral Cl-/HCO3- exchangers and Na+-coupled HCO3- co-transporters (Romero MF et al, 2004; Cordat E and Casey JR, 2009)
The proteins responsible for the exchange of Cl- with HCO3- are members of the SLC4 (1-3) and SLC26 (3, 4, 6, 7 and 9) transporter families. SLC4A1 (Band 3, AE1, anion exchanger 1) was the first bicarbonate transporter gene to be cloned and sequenced. It is ubiquitous throughout vertebrates and in humans, is the major glycoprotein present on erythrocytes and the basolateral surfaces of kidney cells. Variations in erythroid SLC4A1 determine the Diego blood group system. Mutations in the erythrocyte form of SLC4A1 can cause hereditary spherocytosis type 4 (HSP4; MIM:612653), a disorder leading to haemolytic anaemia (HA). Some mutations in SLC4A1 can cause distal (type1) renal tubular acidosis (dRTA; MIM:179800) (an inability to acidify urine) and dRTA-HA (dRTA with hemolytic anemia) (MIM:611590) (Tanner 2002, Romero et al. 2013)
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