| Desaturation of polyunsaturated fatty acids in Mucor circinelloides and the involvement of a novel membrane-bound malic enzyme. | |
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MedLine Citation:
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PMID: 1425673 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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1. The component fatty acids of the endogenous phospholipids of microsomal preparations of Mucor, when shaken at 30 degrees C, increased in both chain length and in degree of unsaturation. The net effect was the production of gamma-linolenic acid which, over 2 h, increased from 17% to 32% of total fatty acids present. No further significant changes occurred after this time. 2. The major site for desaturation/elongation reactions was at the sn-2 position of PtdIns. PtdCho and PtdEtn were not implicated. 3. Of numerous metabolites and cofactors added to the microsomes, only malate could prolong the elongation/desaturation reactions for up to 6 h. This effect was shown to be due to a membrane-associated malic enzyme [malate dehydrogenase (decarboxylating) NADP+] with the NADPH produced being used in fatty-acid desaturation. 4. Kinetic analysis of cytosolic and microsomal enzymes [both in 0.1% (mass/vol.) Chaps] could not distinguish between them. However, when the microsomal malic enzyme was dialysed to remove Chaps, it lost 90% of activity, although the cytosolic malic enzyme lost only 20% activity. 5. The structural analogue of malate, tartronic acid, which is an inhibitor of malic enzyme, also inhibited the malate-induced stimulation of fatty-acyl group desaturation and elongation in the microsomal membranes. 6. It is concluded that two distinct malic enzymes exist, one soluble and one membrane bound, with similar active sites. Both have different roles in the production of NADPH, for lipid metabolism. The former will produce NADPH for fatty-acid biosynthesis whilst the latter produces NADPH for fatty-acid desaturation. |
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Authors:
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A Kendrick; C Ratledge |
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Publication Detail:
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Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: European journal of biochemistry / FEBS Volume: 209 ISSN: 0014-2956 ISO Abbreviation: Eur. J. Biochem. Publication Date: 1992 Oct |
Date Detail:
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Created Date: 1992-12-03 Completed Date: 1992-12-03 Revised Date: 2007-07-23 |
Medline Journal Info:
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Nlm Unique ID: 0107600 Medline TA: Eur J Biochem Country: GERMANY |
Other Details:
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Languages: eng Pagination: 667-73 Citation Subset: IM |
Affiliation:
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Department of Applied Biology, University of Hull, England. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Cytochrome Reductases
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metabolism Cytochrome-B(5) Reductase Cytochromes b5 / metabolism Cytosol / enzymology Enzyme Stability Fatty Acids, Unsaturated / metabolism* Intracellular Membranes / enzymology Kinetics Malate Dehydrogenase / metabolism* Microsomes / enzymology* Mucor / enzymology* Substrate Specificity Thermodynamics |
| Chemical | |
Reg. No./Substance:
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0/Fatty Acids, Unsaturated; 9035-39-6/Cytochromes b5; EC 1.1.1.37/Malate Dehydrogenase; EC 1.6.2.-/Cytochrome Reductases; EC 1.6.2.2/Cytochrome-B(5) Reductase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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