| Nonenzymatic acetolactate oxidation to diacetyl by flavin, nicotinamide and quinone coenzymes. | |
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MedLine Citation:
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PMID: 8541313 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Acetolactate nonenzymatically reduced flavins, quinones and nicotinamide coenzymes in a time-dependent manner at physiological pH and moderate temperature. In the presence of excess acetolactate, the reduction of FAD and NAD+ followed pseudo-first-order kinetics. The rate of reduction was proportional to the concentration of acetolactate, and the rate constants at 37 degrees C and pH 7.5 were 4.8 x 10(-2) M-1 s-1 and 7.4 x 10(-3) M-1 s-1 for FAD and NAD+, respectively. In contrast, ubiquinone reduction followed pseudo-zero-order kinetics in the presence of excess acetolactate. At 37 degrees C and pH 7.5, the rate of reduction was proportional to the acetolactate concentration, and the apparent rate constant was 8.3 x 10(-6) s-1. In contrast to FAD, the rate of reduction of ubiquinone was higher at low pH. The kinetics of ubiquinone reduction suggested that the rate-limiting step was acetolactate decarboxylation and formation of the enolate anion, whereas the rate of FAD reduction was governed by the second-order reaction of the enolate anion. Following the oxidation, acetolactate was converted to diacetyl. Reduced FAD formed by the reaction with acetolactate generated a low rate of O2 consumption during assays of the oxygenase activity of acetohydroxy acid synthase. The reaction of acetolactate with quinones may provide a mechanism for the nonenzymatic formation diacetyl in whole milk. |
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Authors:
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H S Park; R Xing; W B Whitman |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Biochimica et biophysica acta Volume: 1245 ISSN: 0006-3002 ISO Abbreviation: Biochim. Biophys. Acta Publication Date: 1995 Dec |
Date Detail:
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Created Date: 1996-02-13 Completed Date: 1996-02-13 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0217513 Medline TA: Biochim Biophys Acta Country: NETHERLANDS |
Other Details:
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Languages: eng Pagination: 366-70 Citation Subset: IM |
Affiliation:
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Department of Microbiology, University of Georgia, Athens 30602-2605, USA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Benzoquinones
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metabolism* Chromatography, Thin Layer Diacetyl / metabolism* Flavins / metabolism* Lactates / metabolism* Niacinamide / metabolism* Oxidation-Reduction |
| Chemical | |
Reg. No./Substance:
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0/Benzoquinones; 0/Flavins; 0/Lactates; 106-51-4/benzoquinone; 431-03-8/Diacetyl; 535-17-1/alpha-acetolactate; 98-92-0/Niacinamide |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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