Glucosinolate hydrolysis in Lepidium sativum--identification of the thiocyanate-forming protein.

Department of Biochemistry, Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knöll-Str. 8, D-07745, Jena, Germany.
Plant Molecular Biology (Impact Factor: 4.07). 02/2007; 63(1):49-61. DOI: 10.1007/s11103-006-9071-5
Source: PubMed

ABSTRACT Glucosinolates are a class of thioglycosides found predominantly in plants of the order Brassicales whose function in anti-herbivore defense has been attributed to the products formed by myrosinase-catalyzed hydrolysis upon plant tissue damage. The most common type of hydrolysis products, the isothiocyanates, are toxic to a wide range of organisms. Depending on the glucosinolate side-chain structure and the presence of certain protein factors, other types of hydrolysis products, such as simple nitriles, epithionitriles and organic thiocyanates, can be formed whose biological functions are not well understood. Of the proteins controlling glucosinolate hydrolysis, only epithiospecifier proteins (ESPs) that promote the formation of simple nitriles and epithionitriles have been identified on a molecular level. We investigated glucosinolate hydrolysis in Lepidium sativum and identified a thiocyanate-forming protein (TFP) that shares 63-68% amino acid sequence identity with known ESPs and up to 55% identity with myrosinase-binding proteins from Arabidopsis thaliana, but differs from ESPs in its biochemistry. TFP does not only catalyze thiocyanate and simple nitrile formation from benzylglucosinolate but also the formation of simple nitriles and epithionitriles from aliphatic glucosinolates. Analyses of glucosinolate hydrolysis products in L. sativum autolysates and TFP transcript accumulation revealed an organ-specific regulation of thiocyanate formation. The identification of TFP defines a new family of proteins that control glucosinolate hydrolysis and challenges the previously proposed reaction mechanism of epithionitrile formation. As a protein that promotes the formation of a wide variety of hydrolysis products, its identification provides an important tool for further elucidating the mechanisms of glucosinolate hydrolysis as well as the ecological role and the evolutionary origin of the glucosinolate-myrosinase system.

  • [Show abstract] [Hide abstract]
    ABSTRACT: The chemistry of glucosinolates and their behavior during food processing is very complex. Their instability leads to the formation of a bunch of breakdown and reaction products that are very often reactive themselves. Although excessive consumption of cabbage varieties has been thought for long time to have adverse, especially goitrogenic effects, nowadays, epidemiologic studies provide data that there might be beneficial health effects as well. Especially Brassica vegetables, such as broccoli, radish, or cabbage, are rich in these interesting plant metabolites. However, information on the bioactivity of glucosinolates is only valuable when one knows which compounds are formed during processing and subsequent consumption. This review provides a comprehensive, in-depth overview on the chemical reactivity of different glucosinolates and breakdown products thereof during food preparation.
    Angewandte Chemie International Edition 10/2014; 53(43). DOI:10.1002/anie.201402639 · 11.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Myrosinase (EC found in Brassicaceae plants, is the enzyme responsible for hydrolysis of glucosinolates. As a result a variety of biologically active metabolites are liberated, whose importance in crop protection and especially in cancer chemoprevention is rapidly gaining recognition. The growing practical application of glucosinolate degradation products requires that sensitive and reliable methods of myrosinase activity determination in different types of plant samples are established. With the use of commercial myrosinase prep, we systematically optimised conditions of measurement of this enzyme activity by spectrophotometric and pH-stat methods. The parameters evaluated included: sample preparation, choice of substrate, its concentration, reaction temperature and detection wavelength. Two substrates with different spectral properties were chosen: sinigrin (SIN) and glucotropaeolin (GTL). For both substrates, the best reliability was achieved at reaction temperature of 37 degrees C and substrate concentration of 0.2 mM and 5 mM for spectrophotometric and pH-stat methods, respectively. GTL exhibiting higher absorption at the recommended detection wavelength of 230 nm ensured greater sensitivity of spectrophotometric determination of myrosinase activity in the case of transparent plant samples. GTL seemed to increase also the sensitivity of pH-stat method, however, in this case homogenisation of plant samples turned out to be most important. The optimised conditions were then verified for a range of plant samples. Based on these results, the optimised protocols of myrosinase activity determination for both methods are proposed.
    Industrial Crops and Products 10/2013; 50:58-67. DOI:10.1016/j.indcrop.2013.06.048 · 3.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Seed processing and oil pre-treatment were optimised to improve the yield and quality of biodiesel obtained from Sinapis alba. By using solvent extraction or mechanical pressing followed by solvent extraction, an oil extraction yield greater than 41 wt.% and a de-oiled cake with less than 2 wt.% of oil could be obtained. The oil characterisation showed that erucic acid was the most predominant fatty acid in the oil composition (>50 wt.%). A high phosphorous content (>36 mg/kg) and acid value (>1.5 mg KOH/g) were obtained. To obtain a biodiesel with a high methyl ester content, it was necessary to carry out an oil refining process (acid degumming and chemical de-acidification) followed by a standard transesterification with methanol and sodium methoxide as a catalyst. Finally, the quality of the purified biodiesel was tested according to the EN 14214 and ASTM D6751 standards. The results of this work revealed the possibility of using the oil from Sinapis alba seeds as a suitable source for biodiesel.
    Biomass and Bioenergy 10/2013; 51:83–90. DOI:10.1016/j.biombioe.2013.01.008 · 3.41 Impact Factor