Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pyridoxal 5'-diphospho-5'-adenosine (AP2PL) inhibits lamb kidney (Na,K)-ATPase and that inhibition and covalent modification is blocked by the presence of ATP. After trypsin digestion of the labeled, purified alpha subunit and subsequent peptide mapping of the fluorescently labeled peptides by means of high performance liquid chromatography, the main labeled peptide was further purified and analyzed by amino acid composition analysis and peptide sequencing. The obtained peptide had the sequence Ile470-Val-Glu-Ile-Pro-Phe-Asn-Ser-Thr-Asn-Lys480-Tyr-Gln-Le u-Ser-Ile-His- Lys487. Lysine 480 is the residue modified by AP2PL in the absence, but not in the presence of ATP. The beta subunit is not differentially labeled by AP2PL in the presence or absence of ATP. Interestingly, the same results were obtained using pyridoxal phosphate as the labeling and inactivation reagent, indicating that the specificity of labeling by these reagents is not due to the presence of the adenosine moiety, but instead that the initial recognition of nucleotides by the ATP-binding site of (Na,K)-ATPase may be due to recognition of the phosphate moiety. The amino acid sequence surrounding this lysine residue labeled by both reagents is highly conserved in (Na,K)-ATPase and the related (H,K)-ATPase sequences thus far obtained, which may signify a functional importance for this region of the putative ATP-binding site in these transport proteins.
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PMID:Lysine 480 is an essential residue in the putative ATP site of lamb kidney (Na,K)-ATPase. Identification of the pyridoxal 5'-diphospho-5'-adenosine and pyridoxal phosphate reactive residue. 216 43

Daily s.c. injection of gentamicin at either 100 mg/kg for 4 days or 60 mg/kg for 2 weeks produced nephrotoxicity in the adult rat as judged by an increase in urinary excretion of beta-galactosidase, beta-glucuronidase and beta-N-acetylglucosaminidase. The observed enzymuria was associated with significant elevation in total renal phospholipid, phosphatidylinositol, phosphatidylcholine and phosphatidylserine. In addition, gentamicin decreased the activities of renal cortical Na+-K+-adenosine triphosphatase, alkaline phosphatase as well as phospholipase C. Pyridoxal-5'-phosphate (250 mg/kg/day) administered i.p. for 4 or 14 days did not markedly alter the metabolic markers of kidney function. In rats simultaneously given pyridoxal-5'-phosphate and gentamicin for 4 days the vitamin failed to prevent either the antibiotic-induced decrease in renal phospholipase C and alkaline phosphatase or the increase in total renal phospholipid, phosphatidylinositol, phosphatidylcholine and phosphatidylserine. However, simultaneous pyridoxal-5'-phosphate and aminoglycoside treatment for 2 weeks proved effective in blockade of the gentamicin-induced kidney phospholipidosis, elevation in urinary beta-galactosidase, beta-glucuronidase and beta-N-acetylglucosaminidase, as well as reduction in renal phospholipase C and alkaline phosphatase. The gentamicin-induced nephrotoxicity was associated with a decrease in renal pyridoxal-5'-phosphate levels. In the simultaneous 4-day-treated rat the renal concentration of pyridoxal-5'-phosphate returned to approximate control values, whereas after 2 weeks the level of vitamin B6 was approximately 2-fold higher than control. Although pyridoxal-5'-phosphate in the simultaneous group lowered kidney gentamicin content by 40% after 4 or 14 days, protection from aminoglycoside-induced nephrotoxicity was apparent only after 2 weeks in our study.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of gentamicin-induced nephrotoxicity by pyridoxal-5'-phosphate in the rat. 249 42

Pyridoxal isonicotinoyl hydrazone (PIH) has recently been identified as a new iron chelating agent with a high degree of iron mobilizing activity in vitro and in vivo which makes this compound a candidate drug in the treatment of iron overload. This study was undertaken to elucidate the mechanism of action of the iron mobilizing activity of PIH at the cellular level. An in vitro system of rabbit reticulocytes with a high level of non-heme 59Fe was used as a model of iron overload. The effects of various biochemical and physiological maneuvers on the mobilization of 59Fe by PIH from the cells were studied. The fate of [14C]-PIH in the in vitro system was also studied. Studies were also carried out using a crude mitochondrial fraction. The results indicate three phases in the iron mobilizing activity of PIH: (1) the entry of PIH into erythroid cells seems to be by passive diffusion; (2) chelation occurs mainly from mitochondria and may depend on the availability of iron in a low molecular weight, non-heme pool. Chelation seems to be enhanced by reduction of Fe (III) to Fe (II); (3) the exit of the PIH2-Fe complex is an energy-dependent process. Iron mobilization by PIH is not dependent on (Na+ + K+)-ATPase activity, external ionic composition, or external hydrogen ion concentration. Membrane fluidity does not seem to play a role in PIH-Fe mobilization. The exit of the PIH2-Fe complex is inhibited by anti-microtubule agents (vinca alkaloids but not colchicine) suggesting that the PIH2-Fe complex is actively extruded from the cell by a microtubule-dependent event.
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PMID:A study of the mechanism of action of pyridoxal isonicotinoyl hydrazone at the cellular level using reticulocytes loaded with non-heme 59Fe. 684 79

Pig and dog kidney Na+,K+-ATPase preparations, irrespective of specific activity, showed approximately 0.5 mol of maximum phosphorylation/mol alpha-chain for ATP or acetyl phosphate (AcP) at steady state conditions. Pyridoxal 5'-diphospho-5'-adenosine (AP2PL)-treated pig kidney enzymes containing approximately 0.5 mol of AP2PL probe at Lys-480/mol (Tsuda, T., Kaya, S., Funatsu, H., Hayashi, Y., and Taniguchi, K. (1998) J. Biochem. (Tokyo) 123, 169-174) showed a quarter-site phosphorylation by ATP and half-site phosphorylation from AcP. The addition of 10 microM ATP to the Mg2+-Na+-bound AP2PL enzyme induced rapid quarter-site phosphorylation (47/s), followed by two different AP2PL fluorescence changes, a rapid decrease (29/s) and a slow increase (1.1/s). The addition of 1 mM AcP to the Mg2+-Na+-bound AP2PL enzyme induced a slow half-site phosphorylation (3/s), followed by a monophasic AP2PL fluorescence increase (1.2/s). After treatment of the AP2PL enzyme with fluorescein 5'-isothiocyanate to modify Lys-501 fully, the Mg2+-Na+-dependent phosphorylation capacity from ATP of the resulting AP2PL-fluorescein 5'-isothiocyanate enzyme was reduced to approximately 6% without significant changes in half-site phosphorylation capacity with respect to AcP, dynamic AP2PL fluorescence change by ATP and change by AcP. These data and others support the hypothesis that the functional membrane-bound Na+, K+-ATPase has tetrameric properties.
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PMID:Half-site modification of Lys-480 of the Na+,K+-ATPase alpha-chain with pyridoxal 5'-diphospho-5'-adenosine reduces ATP-dependent phosphorylation stoichiometry from half to a quarter. 973 20

1. Intracellular microelectrodes were used to record the transmembrane potential and excitatory junction potentials (e.j.p.s) produced by sympathetic nerve stimulation (1 Hz) in smooth muscle cells of the guinea-pig isolated vas deferens. 2. The symmetrical 3'-urea of 8-(benzamido)naphthalene-1,3,5-trisulphonic acid (NF023) produced a concentration-dependent inhibition of e.j.p. magnitude (IC(50)=4. 8x10(-6) M), but had no effect on the resting membrane potential of the smooth muscle cells. 3. Pyridoxal-5-phosphate (P-5-P) also depressed e.j.p. magnitude in a concentration-dependent manner, but was less potent than NF023 (IC(50)=2.2x10(-5) M). At 10(-4) M and above P-5-P significantly depolarized the smooth muscle cells. 4. The nucleoside triphosphatase inhibitor 6-N,N-diethyl-D-beta, gamma-dibromomethyleneATP (ARL 67156) (5x10(-5) M) significantly increased e.j.p. amplitude. ARL 67156 (10(-4) M) further increased e. j.p. amplitude such that they often reached threshold for initiation of action potentials, causing muscle contraction and expulsion of the recording electrode. 5. After reduction of e.j.p.s by NF023 or P-5-P (both 10(-5) M), subsequent co-addition of ARL 67156 (10(-4) M) significantly increased their magnitude. 6. The overflow of endogenous ATP evoked by field stimulation of sympathetic nerves (8 Hz, 1 min) was measured by HPLC and flurometric detection. ARL 67156 (10(-4) M) enhanced ATP overflow by almost 700% compared to control. 7. We conclude that for electrophysiological studies NF023 is preferable to other P2X receptor antagonists such as pyridoxalphosphate -6-azophenyl-2',4'-disulphonic acid (PPADS), suramin or P-5-P. Furthermore, breakdown of endogenous ATP by nucleoside triphosphatases is an important modulator of purinergic neurotransmission in the guinea-pig vas deferens.
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PMID:The effect of P2 receptor antagonists and ATPase inhibition on sympathetic purinergic neurotransmission in the guinea-pig isolated vas deferens. 1072 56

Recent studies indicate that effects of ATP on unmyelinated afferent nerve fibres contribute to the transduction of nociceptive and non-nociceptive stimuli. In the present study, effects of ATP were studied on axons and Schwann cells of C fibres in isolated rat vagus nerves. A combination of a computerised threshold tracking technique with photometric and confocal measurements of the free intracellular Ca2+ concentration revealed differences in the effect of ATP and related compounds. Pyridoxal-phosphate-6-azophenyl-2',5'-disulphonic acid (iso-PPADS, an antagonist of ionotropic P2X receptors) completely blocked the excitatory effect of alpha,beta-meATP on unmyelinated axons, whereas the effects of ATP and 2-Cl-ATP were only slightly changed. Moreover, the threshold lowering effects of ATP and 2-Cl-ATP, but not of alpha,beta-meATP, were accompanied by intracellular Ca2+ transients. In confocal imaging experiments, the lectin IB4 was used to identify unmyelinated nerve fibres and their ensheathing Schwann cells. The Schwann cells were identified as the cellular elements underlying ATP-induced Ca2+ transients. In addition, an increase in axonal excitability of C fibres was seen during a rise in [Ca2+]i induced by inhibition of the endoplasmic Ca2 ATPase with cyclopiazonic acid. These data show that an increase of the extracellular ATP concentration in an intact peripheral nerve trunk activates both axons and Schwann cells. It appears that P2 nucleotide receptors on Schwann cells may contribute to the excitatory effect of ATP observed on unmyelinated, including nociceptive, axons.
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PMID:ATP affects both axons and Schwann cells of unmyelinated C fibres. 1137 7