Document Detail


Characterization of the Formation of Branched Short-Chain Fatty Acid:CoAs for Bitter Acid Biosynthesis in Hop Glandular Trichomes.
MedLine Citation:
PMID:  23300257     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Bitter acids, well known for the beer flavoring and their diverse biological activities, are predominantly formed in hop (Humulus lupulus) glandular trichomes. Branched short-chain acyl-CoAs (e.g. isobutyryl-CoA, isovaleryl-CoA and 2-methylbutyryl-CoA), derived from the degradation of branched-chain amino acids (BCAA), are essential building blocks for the biosynthesis of bitter acids in hop. However, little is known what components are needed to produce and maintain the pool of branched short-chain acyl-CoAs in hop trichomes. Here, we present evidences at different facets to reveal that both CoA ligases and thioesterases probably involved in bitter acid biosynthesis. Recombinant HlCCL2 protein has high specific activity to isovaleric acid, with Kcat/Km = 4,100 s-1M-1, while recombinant HlCCL4 protein specifically recognize isobutyric acid (Kcat/Km = 1,800 s-1M-1) and 2-methylbutyric acid (Kcat/Km = 6,900 s-1M-1) as substrates. Both HlCCLs, like hop valerophenone synthase (HlVPS), express strongly in glandular trichome and localized to the cytoplasm. Co-expression of HlCCL2 and HlCCL4 with HlVPS in yeast strain leads to a significant high production of acylphloroglucinols (the direct precursors for bitter acid biosynthesis), which further confirm the biochemical function of these two HlCCLs in vivo. Functional identification of one thioesterase which catalyze the reverse reaction of CCLs in mitochondria, together with the comprehensive analysis of genes involved BCAA catabolism, support the requirement of cytosolic CoA ligases for linking BCAA degradation and bitter acid biosynthesis in glandular trichomes. The evolution and other possible physiological roles of branched short-chain fatty acid: CoA ligases in planta are also discussed.
Authors:
Haiyang Xu; Fengxia Zhang; Baoxiu Liu; David V Huhman; Lloyd W Sumner; Richard A Dixon; Guodong Wang
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-8
Journal Detail:
Title:  Molecular plant     Volume:  -     ISSN:  1752-9867     ISO Abbreviation:  Mol Plant     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-9     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101465514     Medline TA:  Mol Plant     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
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