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Characterization of the Formation of Branched Short-Chain Fatty Acid：CoAs for Bitter Acid Biosynthesis in Hop Glandular Trichomes

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Molecular Plant 2013年第4期6卷 1301-1317页

作者： Haiyang Xu Fengxia Zhang Baoxiu Liu David V. Huhman lloyd w. sumner Richard A. Dixon Guodong w.ng 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 University of Chinese Academy of Sciences Beijing 100039 China The Samuel Roberts Noble Foundation Plant Biology 2510 Sam Noble Parkway Ardmore OK 73401 USA Current address: Department of Biological Sciences University of North Texas Denton Texas 76203 USA

Bitter acids, know. for their use as beer flavoring and for their diverse biological activities, are predominantly formed in hop （Humulus lupulus） glandular trichomes. Branched short-chain acyI-CoAs （e.g. isobutyryI-CoA, isovaleryl- CoA and 2-methylbutyryI-CoA）, derived from the degradation of branched-chain amino acids （BCAAs）, are essential building blocks for the biosynthesis of bitter acids in hops. How.ver, little is know. regarding w.at components are needed to produce and maintain the pool of branched short-chain acyI-CoAs in hop trichomes. Here, w. present several lines of evidence that both CoA ligases and thioesterases are likely involved in bitter acid biosynthesis. Recombinant HICCL2 （carboxyl CoA ligase） protein had high specific activity for isovaleric acid as a substrate （Kcat/Km = 4100 s-~ M-l）, w.ereas recombinant HICCL4 specifically utilized isobutyric acid （Kcat/Km = 1800 s-1 M-1） and 2-methylbutyric acid （Kcat/ Km = 6900 s-1 M-~） as substrates. Both HICCLs, like hop valerophenone synthase （HIVPS）, w.re expressed strongly in glandular trichomes and localized to the cytoplasm. Co-expression of HICCL2 and HICCL4 w.th HIVPS in yeast led to significant production of acylphloroglucinols （the direct precursors for bitter acid biosynthesis）, w.ich further confirmed the biochemical function of these tw. HICCLs in vivo. Functional identification of a thioesterase that catalyzed the reverse reaction of CCLs in mitochondria, together w.th the comprehensive analysis of genes involved BCAA catabolism, supported the idea that cytosolic CoA ligases are required 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.

关键词： CoA ligase glandular trichomes bitter acid thioesterase evolution Humulus lupulus

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Protein Precipitation to Remove Carbohydrates that Interfere in Protein-Bound Tryptophan Quantification in Soybean Seeds

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Journal of Analysis and Testing 2020年第3期4卷 238-247页

作者： Zhentian Lei Santosh Kumar Saurav J.Sarma Ritesh Kumar Barbara w.sumner Minviluz G.Stacey lloyd w.sumner University of Missouri Metabolomics Center ColumbiaMO 65211USA Division of Biochemistry University of MissouriColumbiaMO 65211USA Division of Plant Sciences University of MissouriColumbiaMO 65211USA

Tryptophan is one of the nine essential amino acids in humans that can only be obtained through diets and *** is a precursor to many biological processes,such as serotonin,melatonin,kynurenin,and niacin(nicotinamide)vitamin *** content of tryptophan in foods,such as soybean is an important indicator of nutritional ***,accurate quantification of tryptophan in soybean is crucial to soybean nutritional *** of soybean protein-bound amino acids first involves acid hydrolysis of total protein to liberate amino ***,tryptophan quantification follow.ng acid hydrolysis is difficult or impossible due to its reactions w.th soybean ***,removal of carbohydrates from soy proteins prior to acid hydrolysis is *** this study,w. compared four common protein precipitation methods(i.e.,methanol,acetonitrile,acetone,and trichloroacetic acid(TCA)protein precipitation methods)to determine the best method to separate soy proteins from carbohydrates,and concluded that acetone provided the highest recovery of soy *** content in the precipitated proteins w.s determined after acid hydrolysis of the proteins using liquid chromatography-tandem mass spectrometry multiple reaction monitoring(LC-MS/MS-MRM).No significant difference in the tryptophan content w.s found among proteins precipitated w.th methanol,acetonitrile,and TCA,suggesting that these precipitated proteins have similar compositions.A slightly low.r,but statistically significant tryptophan content w.s found in the acetonitrile-precipitated proteins,suggesting that these proteins contain slightly higher glycosylated proteins.

关键词： Tryptophan Acid hydrolysis LC-MS/MS MRM Soybean seeds Protein precipitation

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豆奶甲醇提取物中抗氧化活性物质的鉴定

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现代食品科技 2013年第8期29卷 1999-2003页

作者：张华 sumner lloyd LEI Zhen-tian HUHMAN David w.TSON Bonnie 付福友于杰西南大学园艺园林学院重庆北碚400715 The Samuel Roberts Noble Foundation 俄克拉荷马州阿德莫尔市73401 加拿大农业与农业食品部萨斯卡通SK S7N0X2 南方山地园艺教育部重点实验室重庆北碚400715

本文主要在研究了豆奶甲醇提取物有无抗氧化活性的基础上,分析鉴定了其可能存在的抗氧化物质,为相关研究提供理论依据。测定抗氧化能力的方法包括1,1-二苯基-2-三硝基苯肼(1,1-Diphenyl-2-picrylhydrazyl radical,DPPH)法和铁离子还原能... 详细信息

本文主要在研究了豆奶甲醇提取物有无抗氧化活性的基础上,分析鉴定了其可能存在的抗氧化物质,为相关研究提供理论依据。测定抗氧化能力的方法包括1,1-二苯基-2-三硝基苯肼(1,1-Diphenyl-2-picrylhydrazyl radical,DPPH)法和铁离子还原能力(Ferricreducing antioxidant pow.r,FRAP)法。比色法测定总酚含量和总黄酮含量。通过超高效液相-四极杆飞行时间串联质谱(Ultra-highperformance liquid chromatography-quadruple time-of-flight-mass spectrometry,UHPLC-QTOF-MS)测定豆奶甲醇提取液中活性成分的种类和含量。实验表明,豆奶甲醇提取液具有一定的抗氧化性,且DPPH法和FRAP法测定豆奶抗氧化值不存在显著性差异。豆奶甲醇提取物的总酚含量(285.77±2.93μg/mL)远高于总黄酮含量(11.27±0.51μg/mL)。鉴定出5种化合物,其中只有6,7,4'-三羟基黄酮和Rha-Ara-GlcA-SoyB与抗氧化值存在正相关性。异黄素和大豆甙元两种异黄酮与抗氧化值存在着负相关,6,7,4'-三羟基黄酮可能是主要的抗氧化物质。

关键词：豆奶抗氧化性 DPPH法 FRAP法总酚含量总黄酮含量

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