Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined the protein and mRNA encoding the amiloride-sensitive Na+/H+ exchanger from human placenta. Reverse transcriptase PCR of human placental RNA and a human choriocarcinoma cell line showed that the message for the amiloride-sensitive Na+/H+ exchanger from human placenta. Reverse transcriptase PCR of human placental RNA and a human choriocarcinoma cell line showed that the message for the amiloride-sensitive Na+/H+ exchanger is present in the placenta and its derived cell line. Northern blot analysis showed only one species of Na+/H+ exchanger mRNA, of about 5 kb in size. To examine the Na+/H+ exchanger protein two different affinity-purified antibodies were produced against the C-terminal cytoplasmic region of the Na+/H+ exchanger. The antibodies both identified a 105 kDa protein in human placental brush border membrane vesicles. Under non-reducing conditions the amount of 105 kDa protein was greatly decreased, while a 205 kDa protein became apparent. This is probably a dimer of the 105 kDa protein. The monomer-to-dimer transition was dependent on the concentration of beta-mercaptoethanol. The results show that the amiloride-sensitive Na+/H+ exchanger is relatively abundant in human placenta and that it can exist as a larger 205 kDa protein linked by disulphide bonds.
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PMID:Characterization of the placental brush border membrane Na+/H+ exchanger: identification of thiol-dependent transitions in apparent molecular size. 838 Sep 78

Sulphotransferases are a family of enzymes involved in the metabolism and detoxification of many compounds. Dehydroepiandrosterone (DHEA) sulphotransferase (DHEA-ST), which catalyzes the sulphation of steroids such as DHEA, is present in rat liver and adrenals. Sulphated steroids are present in urine, and many other enzymes which catalyze detoxification reactions are found in the kidney. There are not previous reports of DHEA-ST localization in adult kidney. The activity of DHEA-ST was investigated in adult rat kidney by a radio-isotope assay with DHEA as the substrate. Western blotting was used to assess protein expression, and the localization of DHEA-ST was investigated by immunohistochemistry. The DHEA-ST activity in rat kidney was found to be approximately four times less than that in rat liver. In female kidney, the activity was 1.46 +/- 0.06 nmol/min/microg, and in male kidney the activity was 1.29 +/- 0.09 nmol/min/microg. Investigation of protein expression gave a single band at 35 kDa which signified the presence of this enzyme in both male and female adult rat kidneys. Localization studies showed positive staining at high intensity in the collecting ducts of the medulla and in the S3 portion of the proximal convoluted tubule in the cortex. The distribution within the proximal tubules was restricted to the brush border. Reverse-transcriptase polymerase chain reaction showed DHEA-ST RNA expression in adult rat kidney and liver. The presence of this enzyme and its location in the kidney may suggest that in situ sulphation via DHEA-ST may play an important role in the excretion of endogenous and exogenous compounds.
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PMID:Investigation of the localization of dehydroepiandrosterone sulphotransferase in adult rat kidney. 1101 88

A cDNA coding a new H+/organic cation antiporter, human kidney-specific multidrug and toxin extrusion 2 (hMATE2-K), has been isolated from the human kidney. The hMATE2-K cDNA had an open reading frame that encodes a 566-amino acid protein, which shows 94, 82, 52, and 52% identity with the hMATE2, hMATE2-B, hMATE1, and rat MATE1, respectively. Reverse transcriptase-PCR revealed that hMATE2-K mRNA but not hMATE2 was expressed predominantly in the kidney, and hMATE2-B was ubiquitously found in all tissues examined except the kidney. The immunohistochemical analyses revealed that the hMATE2-K as well as the hMATE1 was localized at the brush border membranes of the proximal tubules. HEK293 cells that were transiently transfected with the hMATE2-K cDNA but not hMATE2-B exhibited the H+ gradient-dependent antiport of tetraethylammonium (TEA). Transfection of hMATE2-B had no affect on the hMATE2-K-mediated transport of TEA. hMATE2-K also transported cimetidine, 1-methyl-4-phenylpyridinium (MPP), procainamide, metformin, and N1-methylnicotinamide. Kinetic analyses demonstrated that the Michaelis-Menten constants for the hMATE2-K-mediated transport of TEA, MPP, cimetidine, metformin, and procainamide were 0.83 mM, 93.5 microM, 0.37 mM, 1.05 mM, and 4.10 mM, respectively. Ammonium chloride-induced intracellular acidification significantly stimulated the hMATE2-K-dependent transport of organic cations such as TEA, MPP, procainamide, metformin, N1-methylnicotinamide, creatinine, guanidine, quinidine, quinine, thiamine, and verapamil. These results indicate that hMATE2-K is a new human kidney-specific H+/organic cation antiporter that is responsible for the tubular secretion of cationic drugs across the brush border membranes.
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PMID:Identification and functional characterization of a new human kidney-specific H+/organic cation antiporter, kidney-specific multidrug and toxin extrusion 2. 1680