Phosphate co transporters

Fibroblast growth factor 23 (FGF23) is a single-chain protein with 251 amino acids including a 24-amino-acid leader sequence. It inhibits l,25(OH)2D3 production and phosphate reabsorption (via the sodium phosphate co-transporters NaPi... 

Saito, H., Kusano, K., Kinosaki, M., Ito, H., Hirata, M., Segawa, H., Miyamoto, K. and Fukushima, N. (2003). Human fibroblast growth factor-23 mutants suppress Na+-dependent phosphate co-transport activity and 1 alpha, 25-dihydroxyvitamin D3 production. J. Biol. Chem. 278, 2206-2211. 

V achon, V., Delisle, M.-C., Laprade, R., Beliveau, R. (1991). Reconstitution of the renal brush-border membrane sodium/phosphate co-transporter. Biochem. J. 278,543-548. 

Several disorders of tubular phosphate handhng have been described. The best known of these is X-linked dominant hypophosphatemic rickets (previously known as vitamin D-resistant rickets). This disorder arises because of a defect in the PHEX gene. A defect of the sodium-dependent/ phosphate co-transporter has also been described, giving rise to autosomal recessive hereditary hypophosphatemic rickets with hypercalciuria. The molecular biology of tliese and other renal phosphate transport disorders has been reviewed. ... 

Oberbauer et al. reported inhibition of a sodium/phosphate (Na/Pi-2) co-transporter by phosphorothioated AS-ODN. A single intravenous injection of the AS-ODN inhibited both the mRNA and the protein for the Na/Pi-2 co-transporter, and conseqnently snppressed In-minal uptake of phosphate by the proximal tubules [130],... 

Phosphorus is predominantly absorbed as inorganic phosphate in the upper small intestine. Phosphate is transported into the epithelial cells by co-transport with sodium expression of transport is enhanced by vitamin D. 

Osteoblasts also take up orthophosphate (Pi) from the periosteal extracellular fluid using a type I sodium/Pi co-transporter. Pi consists of about 60% monohydrogen phosphate and 40% dihydrogen phosphate at pH 7.0. The Pi diffuses freely through the cytosol and exits... 

Niacin is a generic term which refers to two related chemical compounds, nicotinic acid (6.22) and its amide, nicotinamide (6.23) both are derivatives of pyridine. Nicotinic acid is synthesized chemically and can be easily converted to the amide in which form it is found in the body. Niacin is obtained from food or can be synthesized from tryptophan (60 mg of dietary tryptophan has the same metabolic effect as 1 mg niacin). Niacin forms part of two important co-enzymes, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are co-factors for many enzymes that participate in various metabolic pathways and function in electron transport. 

Bouwman et al. demonstrated that Pt can be used in the ionic form (Pt" and Pt") by dispersing it in a matrix of hydrous iron phosphate (FePO) via a sol-gel process (Pt-FePO)." The hydrous FePO possesses micropores of approximately 2 nm. It has 3 H2O molecules per Fe atom and is thought to also serve as a proton transport medium. The Pt-FePO catalyst exhibited a higher ORR activity than Pt/C catalysts. This catalyst was also found to be less sensitive to CO poisoning because CO did not adsorb onto the catalyst surface. The ORR catalytic activity was attributed to the adsorption and storage of oxygen on the FePO, presumably as Fe-hydroperoxides. However, these catalysts have poor electrical conductivity. There is no published data on the long-term stability of these catalysts in fuel cell environments. 

In any case, such values of electrochemical parameters for ligands relevant in biology almost from biopoiesis onwards allowed for broad and differentiated use of now essential elements much like in recent biomasses also >2.3 bio. years ago, without the necessity to have specialized transport systems at hand. Possibly, phosphate-containing regulating systems and transporters - besides the more advanced polyphenols, hydroxamates or proteins (chaperons) - involved in transportation of, e.g. Fe are relics of those days. Possible items of such transport include all of the more general essential elements except for Co and V. The edges to the central window of essentiality in the c/x... 

Methanogenesis from acetate in extracts of Methanosarcina does not require membrane addition [260]. However, this does not exclude a function for cytochromes in acetoclastic methanogenesis by whole cells. Rather, the role of H2 in cell extracts, the ability of cytochrome b from Methanosarcina species to react with CO, and the observation that membrane-bound cytochromeb of M. barkeri is reduced by H2, and is oxidized by CH3-CoM -I- ATP or CH3-C0M + acetyl-phosphate, all point to the participation of cytochromes in Methanosarcina. A role of cytochromes in transport of electrons generated from carboxyl-group oxidation to the heterodisulfide reductase is a logical hypothesis. 

Phosphate transporters have been characterized in many model organisms, though relatively little mechanistic work has been done in marine phytoplankton. Phosphate transport is elfected by high and low affinity transporters and dependent on ATP, Na, and Mg " " in several diatoms (Cembella et al., 1984). These observations are found to be consistent with the well known active transport system of yeast (Raghothama, 1999). The dependence of phosphate transport on Mg " " in diatoms and yeast suggests that eukaryotes may transport an uncharged cation phosphate complex (MeHP04, where Me may be Ca +, Mg +, Co +, Mn ) as has been observed in heterotrophic bacteria (van Veen, 1997). 

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