| Transport of L-asparagine in Tetrahymena pyriformis ecto-L-asparaginase is not related to L-asparagine-protein transport system. | |
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MedLine Citation:
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PMID: 1930247 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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L-Asparaginase of T. pyriformis is a membrane-bound enzyme with an active site situated on the outside surface of the membrane. When radioactive L-asparagine was incubated with T. pyriformis cells in the L-asparaginase assay medium, the hydrolysis was 240 higher than the uptake of this amino acid. In a similar experiment performed in salt medium (Wagner's solution), the hydrolysis was linearly increased and reached after one hour of incubation a value of 60 nmol/10(6) cells, while the uptake after 20 min of incubation reached a plateau with a value of 15 nmol/10(6) cells. The uptake of L-leucine under these conditions was 44 nmol/10(6) cells/hr, while no measurable transport of aspartic acid was observed. That L-aspartic acid is not migrated into T. pyriformis cells is in agreement with the finding that no efflux of this amino acid takes place as well. The uptake of L-asparagine is pH and K+ dependent, whereas Na+ ions strongly inhibit this uptake. The Km and Vmax values of L-asparagine uptake is 1.43 mM and 0.7 nmol/min, respectively. The half life of L-asparagine "protein transport system" was 40 min, a value which is very close to the half life of the membrane-bound L-asparaginase of this microorganism. Ouabain and vanadate inhibit the uptake of L-asparagine by more than 80%, while ouabain or vanadate inhibit in vivo 5% or 95% the activity of L-asparaginase, respectively. This indicates the lack of interrelationship between the L-asparagine "protein transport system" and the L-asparaginase protein molecule. |
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Authors:
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I K Tsavdaridis; D J Triantafillou; D A Kyriakidis |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Biochemistry international Volume: 24 ISSN: 0158-5231 ISO Abbreviation: Biochem. Int. Publication Date: 1991 May |
Date Detail:
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Created Date: 1991-11-06 Completed Date: 1991-11-06 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 8100311 Medline TA: Biochem Int Country: AUSTRALIA |
Other Details:
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Languages: eng Pagination: 281-90 Citation Subset: IM |
Affiliation:
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Laboratory of Biochemistry, Faculty of Chemistry, School of Sciences, Aristotelian University of Thessaloniki, Greece. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Asparaginase / metabolism* Asparagine / metabolism* Aspartic Acid / metabolism Biological Transport, Active Hydrogen-Ion Concentration Hydrolysis Kinetics Ouabain / pharmacology Potassium / pharmacology Tetrahymena pyriformis / cytology, enzymology*, growth & development, metabolism Vanadates / pharmacology |
| Chemical | |
Reg. No./Substance:
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0/Vanadates; 56-84-8/Aspartic Acid; 630-60-4/Ouabain; 7006-34-0/Asparagine; 7440-09-7/Potassium; EC 3.5.1.1/Asparaginase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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