| On the control of long-chain-fatty acid synthesis in isolated intact spinach (Spinacia oleracea) chloroplasts. | |
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MedLine Citation:
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PMID: 534525 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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1. Chloroplasts isolated from spinach leaves by using the low-ionic-strength buffers of Nakatani & Barber [(1977) Biochim. Biophys. Acta.461, 510-512] had higher rates of HCO(3) (-)-dependent oxygen evolution (up to 369mumol/h per mg of chlorophyll) and higher rates of [1-(14)C]acetate incorporation into long-chain fatty acids (up to 1500nmol/h per mg of chlorophyll) than chloroplasts isolated by using alternative procedures. 2. Acetate appeared to be the preferred substrate for fatty acid synthesis by isolated chloroplasts, although high rates of synthesis were also measured from H(14)CO(3) (-) in assays permitting high rats of photosynthesis. Incorporation of H(14)CO(3) (-) into fatty acids was decreased by relatively low concentrations of unlabelled acetate. Acetyl-CoA synthetase activity was present 3-4 times in excess of that required to account for rates of [1-(14)C]acetate incorporation into fatty acids, but pyruvate dehydrogenase was either absent or present in very low activity in spinach chloroplasts. 3. Rates of long-chain-fatty acid synthesis from [1-(14)C]acetate in the highly active chloroplast preparations, compared with those used previously, were less dependent on added cofactors, but showed a greater response to light. The effects of added CoA plus ATP, Triton X-100 and sn-glycerol 3-phosphate on the products of [1-(14)C]acetate incorporation were similar to those reported for less active chloroplast preparations. 4. Endogenous [(14)C]acetyl-CoA plus [(14)C]malonyl-CoA was maintained at a constant low level even when fatty acid synthesis was limited by low HCO(3) (-) concentrations. Endogenous [(14)C]acyl-(acyl-carrier protein) concentrations increased with increasing HCO(3) (-) concentration and higher rates of fatty acid synthesis, but were slightly lower in the presence of Triton X-100. It is proposed that rates of long-chain-fatty acid synthesis in isolated chloroplasts at saturating [1-(14)C]acetate concentrations and optimal HCO(3) (-) concentrations may be primarily controlled by rates of removal of the products of the fatty acid synthetase. |
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Authors:
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P G Roughan; R Holland; C R Slack |
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Publication Detail:
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Type: In Vitro; Journal Article |
Journal Detail:
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Title: The Biochemical journal Volume: 184 ISSN: 0264-6021 ISO Abbreviation: Biochem. J. Publication Date: 1979 Nov |
Date Detail:
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Created Date: 1980-03-24 Completed Date: 1980-03-24 Revised Date: 2010-09-02 |
Medline Journal Info:
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Nlm Unique ID: 2984726R Medline TA: Biochem J Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 193-202 Citation Subset: IM |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Acetates
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metabolism Acetyl Coenzyme A / metabolism Acyl Carrier Protein / metabolism Bicarbonates / metabolism Buffers Chloroplasts / enzymology, metabolism* Fatty Acids / biosynthesis* Kinetics Malonyl Coenzyme A / metabolism |
| Chemical | |
Reg. No./Substance:
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0/Acetates; 0/Acyl Carrier Protein; 0/Bicarbonates; 0/Buffers; 0/Fatty Acids; 524-14-1/Malonyl Coenzyme A; 72-89-9/Acetyl Coenzyme A |
| Comments/Corrections | |
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