Document Detail

O-Methylation of benzaldehyde derivatives by "lignin specific" caffeic acid 3-O-methyltransferase.
MedLine Citation:
PMID:  15081283     Owner:  NLM     Status:  MEDLINE    
Although S-adenosyl-l-methionine (SAM) dependent caffeic acid/5-hydroxyferulic acid 3/5-O-methyltransferase (COMT) is one of the key enzymes in lignin biosynthesis, the present work demonstrates that alfalfa COMT methylates benzaldehyde derivatives more efficiently than lignin pathway intermediates. 3,4-Dihydroxy, 5-methoxybenzaldehyde and protocatechuic aldehyde were the best in vitro substrates for OMT activity in extracts from developing alfalfa stems, and these compounds were preferred over lignin pathway intermediates for 3-O-methylation by recombinant alfalfa COMT expressed in Escherichia coli. OMT activity with benzaldehydes was strongly reduced in extracts from stems of transgenic alfalfa down-regulated in COMT. However, although COMT down-regulation drastically affects lignin composition, it does not appear to significantly impact metabolism of benzaldehyde derivatives in alfalfa. Structurally designed site-directed mutants of COMT showed altered relative substrate preferences for lignin precursors and benzaldehyde derivatives. Taken together, these results indicate that COMT may have more than one role in phenylpropanoid metabolism (but probably not in alfalfa), and that engineered COMT enzymes could be useful for metabolic engineering of both lignin and benzaldehyde-derived flavors and fragrances.
Parvathi Kota; Dianjing Guo; Chloe Zubieta; Joe Noel; Richard A Dixon
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Phytochemistry     Volume:  65     ISSN:  0031-9422     ISO Abbreviation:  Phytochemistry     Publication Date:  2004 Apr 
Date Detail:
Created Date:  2004-04-14     Completed Date:  2004-07-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0151434     Medline TA:  Phytochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  837-46     Citation Subset:  IM    
Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA.
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MeSH Terms
Amino Acid Substitution
Benzaldehydes / chemistry,  metabolism*
Carbon Radioisotopes
Hydroxybenzoic Acids / chemistry,  metabolism
Lignin / metabolism*
Medicago sativa / enzymology,  genetics
Methyltransferases / genetics,  metabolism*
Phenols / chemistry,  metabolism
Plant Stems / enzymology
Plants, Genetically Modified / enzymology
Recombinant Proteins / genetics,  metabolism
S-Adenosylmethionine / metabolism
Substrate Specificity
Reg. No./Substance:
0/Benzaldehydes; 0/Carbon Radioisotopes; 0/Hydroxybenzoic Acids; 0/Phenols; 0/Recombinant Proteins; 29908-03-0/S-Adenosylmethionine; 9005-53-2/Lignin; 99-50-3/protocatechuic acid; EC 2.1.1.-/Methyltransferases; EC O-methyltransferase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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