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H,K ATPase, gastric

FIGURE 10.13 Some of the sequence homologies in the nucleotide binding and phosphorylation domains of Na, K -ATPase, Ca -ATPase, and gastric H, K -ATPase. (Adapted from j0rgensm, P. L., and Andersen, J. R, 1988. Structnral basis for Ei - E2 confoyinational transitions in Na, K -pnmp and Cc -pnmp proteins. Journal of Membrane Biology 103 95-120)... [Pg.305]

Tlie Na+/K+-ATPase belongs to the P-type ATPases, a family of more than 50 enzymes that also includes the Ca2+-ATPase of the sarcoplasmic reticulum or the gastric H+/K+-ATPase. P-Type ATPases have in common that during ion transport an aspartyl phos-phointermediate is formed by transfer of the y-phosphate group of ATP to the highly conserved sequence DKTGS/T [1]. [Pg.813]

Gastric H,K-ATPase inhibitors Potassium competitive acid blockers... [Pg.1031]

The proton pump is the gastric H,K-ATPase, which secretes hydronium ions, H30+, in exchange forK+ into the secretory canaliculus generating a pH of <1.0 in... [Pg.1031]

Proton Pump Inhibitors and Acid Pump Antagonists. Figure 2 Chemical mechanism of irreversible PPIs. PPIs are accumulated in acidic lumen and converted to active sulfenic acid and/or sulfenamide by acid catalysis. These active forms bind to extracytoplasmic cysteines of the gastric H.K-ATPase [3]. [Pg.1033]

Shin JM, Cho YM, Sachs G (2004) Chemistry of covalent inhibition of the gastric (H+,K+)-ATPase by proton pump inhibitors. J Am Chem Soc 126 7800-7811... [Pg.1035]

Shin JM, S achs G (2004) Differences in binding properties of two proton pump inhibitors on the gastric H+,K+-ATPase in vivo. Biochem Pharmacol 68 2117-2127... [Pg.1035]

In this chapter we will review the recent investigations of the structure of both the a and P subunit, and the function of gastric H,K-ATPase. We will proceed from a brief overview of the tissue distribution to a successive discussion of structure, kinetics, transport properties, lipid dependency, solubilization and reconstitution, and inhibitors of H,K-ATPase that may label functionally important domains of the enzyme. [Pg.28]

Until recently, the possibility that H,K-ATPase consists not only of a catalytic a subunit but also of other subunits was not examined. This was mainly due to the fact that SDS-PAGE of purified gastric H,K-ATPase preparations principally gave one protein band with an apparent molecular mass of about 100 kDa, which was reported to comprise 75% or more of the total amount of protein [6,66,67]. This mass is lower than the mass deduced from its cloned cDNA [40], but may be due to the higher electrophoretic mobility of membrane-bound proteins, as consequence of having relatively high contents of hydrophobic amino acid residues [68]. [Pg.31]

Gastric H,K-ATPase catalyses the 1 1 exchange of H for K upon hydrolysis of ATP, which results in vivo in a pH difference of more than six between the cytoplasm and the lumen [4-6]. Several reaction schemes have been developed to account for the hydrolysis of ATP and the transport of H and K" [14,104-107]. The basis for all these schemes is the Albers-Post scheme originally postulated for the mechanism of action of Na,K-ATPase [108,109]. [Pg.36]

Like Na,K-ATPase, gastric H,K-ATPase also exhibits a p-nitrophenylphosphatase (/>NPPase) activity. This phosphatase activity is dependent on Mg and K, or one of its congeners with the same order of selectivity as for the ATPase activity, yielding a specific activity of 6D84% of the maximal ATPase activity [4,136,137]. Phosphorylation by pNPP has not been demonstrated and transport is also not catalyzed by this substrate. As in the ATPase reaction the effect of on the... [Pg.40]

ATPase also catalyzed a passive Rb -Rb exchange, the rate of which was comparable to the rate of active Rb efflux. This suggested that the K-transporting step of H,K-ATPase is not severely limited by a K -occluded enzyme form, as was observed for Na,K-ATPase. Skrabanja et al. [164] also described the reconstitution of choleate solubilized H,K-ATPase into phosphatidylcholine-cholesterol liposomes. With the use of a pH electrode to measure the rate of H transport they observed not only an active transport, which is dependent on intravesicular K, but also a passive H exchange. This passive transport process, which exhibited a maximal rate of 5% of the active transport process, could be inhibited by vanadate and the specific inhibitor omeprazole, giving evidence that it is a function of gastric H,K-ATPase. The same authors demonstrated, by separation of non-incorporated H,K-ATPase from reconstituted H,K-ATPase on a sucrose gradient, that H,K-ATPase transports two protons and two ions per hydrolyzed ATP [112]. [Pg.46]

The search for specific inhibitors of gastric H,K-ATPase has a dual purpose. First, with the help of suitable inhibitors it is possible to get insight into the molecular mechanisms of H,K-ATPase, and second, a specific inhibitor might be clinically useful for inhibition of gastric acid secretion in anti-ulcer therapy. [Pg.46]

GABA, heterocyclic analogues, 22 (1985) 67 GABAa receptor ligands, 36 (1999) 169 Gas-liquid chromatography and mass spectrometry, 12 (1975) 1 Gastric H /K -ATPase inhibitors, 31 (1994) 233... [Pg.388]

This class of enzymes [EC 3.6.1.36] (also known as the hydrogen/potassium-exchanging ATPase, the potassium-transporting ATPase, proton pump, and the gastric H+/K+ ATPase) catalyzes the hydrolysis of ATP to ADP and orthophosphate, coupled with the exchange of and ions. The gastric mucosal enzyme has been the best characterized. [Pg.72]

Lindberg et al. [169] proposed a mechanism of action for omeprazole, the inhibitor of the gastric H+/K+-ATPase, which is responsible for the gastric acid production and located in the secretory membranes of the parietal cell. Omeprazole itself is not an active inhibitor of this enzyme,... [Pg.250]

Chemomechanical coupling in the gastric H,K ATPase. Acta Physiol. Scand. 146,77-88. Bigelow, DJ. Inesi, G. (1992). Contributions of chemical derivatization and spectroscopic studies to the characterization of the Ca+ transport ATPase of sarcoplasmic reticulum. Biochim. Biophys. Acta 1113, 323-338. [Pg.60]

Polvani, C., Sachs, G Blostein, R. (1989). Sodium ions as substitutes for protons in the gastric H,K-ATPase. J. Biol. Chem. 264, 17854-17859. [Pg.64]


See other pages where H,K ATPase, gastric is mentioned: [Pg.307]    [Pg.25]    [Pg.524]    [Pg.1032]    [Pg.1492]    [Pg.27]    [Pg.27]    [Pg.28]    [Pg.28]    [Pg.32]    [Pg.38]    [Pg.39]    [Pg.40]    [Pg.41]    [Pg.42]    [Pg.42]    [Pg.43]    [Pg.44]    [Pg.45]    [Pg.46]    [Pg.47]    [Pg.47]    [Pg.49]    [Pg.357]    [Pg.220]    [Pg.1046]    [Pg.612]    [Pg.387]    [Pg.130]    [Pg.26]    [Pg.33]    [Pg.40]   
See also in sourсe #XX -- [ Pg.612 ]

See also in sourсe #XX -- [ Pg.25 , Pg.612 ]




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