Document Detail

When quinones meet amino acids: chemical, physical and biological consequences.
MedLine Citation:
PMID:  16601927     Owner:  NLM     Status:  MEDLINE    
Quinones and amino acids are usually compartmentally separated in living systems, however there are several junctions in which they meet, react and influence. It occurs mainly in wounded, cut or crushed plant material during harvest, ensiling or disintegrating cells. Diffusing polyphenols are oxidized by polyphenol oxidases (PPOs) to quinonic compounds, which associate reversibly or irreversibly with amino acids and proteins. The reaction takes place with the free nucleophilic functional groups such as sulfhydryl, amine, amide, indole and imidazole substituents. It results in imine formation, in 1,4-Michael addition via nitrogen or sulphur and in Strecker degradation forming aldehydes. The formation and activity of quinone-amino acids conjugates influences the colour, taste, and aroma of foods. Physical and physiological phenomena such as browning of foods, discoloration of plants during processing, alteration of solubility and digestibility, formation of humic substances, germicidal activity, cytotoxicity and more occur when quinones from disintegrating cells meet amino acids. The mechanisms of toxicity and the pathways by which PCBs may be activated and act as a cancer initiator include oxidation to the corresponding quinones and reaction with amino acids or peptides. Sclerotization of insect cuticle is a biochemical process involving also the reaction between quinones and amino acid derivatives.
S Bittner
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Publication Detail:
Type:  Journal Article; Review     Date:  2006-04-13
Journal Detail:
Title:  Amino acids     Volume:  30     ISSN:  0939-4451     ISO Abbreviation:  Amino Acids     Publication Date:  2006 May 
Date Detail:
Created Date:  2006-05-08     Completed Date:  2006-11-28     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9200312     Medline TA:  Amino Acids     Country:  Austria    
Other Details:
Languages:  eng     Pagination:  205-24     Citation Subset:  IM    
Department of Chemistry, Ben Gurion University of the Negev, Beer Sheva, Israel.
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MeSH Terms
Amino Acids / chemistry*,  metabolism,  toxicity
Catechol Oxidase / chemistry,  metabolism,  toxicity
Flavonoids / chemistry*,  metabolism,  toxicity
Food Analysis
Maillard Reaction
Phenols / chemistry*,  metabolism,  toxicity
Plants / chemistry,  metabolism
Quinones / chemistry*,  metabolism
Reg. No./Substance:
0/Amino Acids; 0/Flavonoids; 0/Phenols; 0/Quinones; 0/polyphenols; EC Oxidase

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