Adenine and hypoxanthine transport in human erythrocytes: distinct substrate effects on carrier mobility
| Autor: | Peter Chiba, Werner Kommer, Richard Marz, Mehrdad Baghestanian, Mehrdad Razavi, Gerhard Prager, Martin Kraupp |
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| Rok vydání: | 1991 |
| Předmět: |
Erythrocytes
Stereochemistry Biophysics In Vitro Techniques Biochemistry Nucleobase Substrate Specificity chemistry.chemical_compound Reference Values Humans Hypoxanthine biology Chemistry Membrane transport protein Adenine Hypoxanthine transport Substrate (chemistry) Biological Transport Cell Biology Membrane transport Kinetics Hypoxanthines Adenine transport biology.protein Carrier Proteins Sulfanilic acid |
| Zdroj: | Biochimica et biophysica acta. 1070(1) |
| ISSN: | 0006-3002 |
| Popis: | Transport of adenine and hypoxanthine in human erythrocytes proceeds via two mechanisms: (1) a common carrier for both nucleobases and (2) unsaturable permeation 4-5-fold faster for adenine for hypoxanthine. The latter process was resistant to inactivation by diazotized sulfanilic acid. Carrier mediated transport of both substrates was investigated using zero-trans and equilibrium exchange protocols. Adenine displayed a much higher affinity for the carrier (Km approximately 5-8 microM) than hypoxanthine (Km approximately 90-120 microM) but maximum fluxes at 25 degrees C were generally 5-10-fold lower for adenine (Vmax approximately 0.6-1.4 pmol/microliters per s) than for hypoxanthine (Vmax approximately 9-11 pmol/microliters per s). The carrier behaved symmetrically with respect to influx and efflux for both substrates. Adenine, but not hypoxanthine reduced carrier mobility more than 10-fold. The mobility of the unloaded carrier, calculated from the kinetic data of either hypoxanthine or adenine transport, was the same thus providing further evidence that these substrates share a common transporter and that their membrane transport is adequately described by the alternating conformation model of carrier-mediated transport. |
| Databáze: | OpenAIRE |
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