Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.21 (beta-glucosidase)
 3,280 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cyanogenic glycosides belong to the products of secondary metabolism, to the natural products of plants. These compounds are composed of an alpha-hydroxynitrile type aglycone and of a sugar moiety (mostly D-glucose). The distribution of the cyanogenic glycosides (CGs) in the plant kingdom is relatively wide, the number of CG-containing taxa is at least 2500, and a lot of such taxa belong to families Fabaceae, Rosaceae, Linaceae, Compositae and others. Different methods of determination are discussed (including the indirect classical photometrical and the new direct chromatographic ones). The genetic control of cyanogenesis has no unique mechanism, the plants show variation in the amount of the produced HCN. The production of HCN depends on both the biosynthesis of CGs and on the existence (or absence) of its degrading enzymes. The biosynthetic precursors of the CGs are different L-amino acids, these are hydroxylated then the N-hydroxylamino acids are converted to aldoximes, these are turned into nitriles. The last ones are hydroxylated to alpha-hydroxynitriles and then they are glycosilated to CGs. The generation of HCN from CGs is a two step process involving a deglycosilation and a cleavage of the molecule (regulated by beta-glucosidase and alpha-hydroxynitrilase). The tissue level compartmentalisation of CGs and their hydrolysing enzymes prevents large-scale hydrolysis in intact plant tissue. The actual level of CGs is determined by various factors both developmental and ecological ones, which are reviewed too. The last part of the present work demonstrates the biological roles of CGs in plant physiological processes and in plant defence mechanisms as well. The effect of CGs (HCN) on different animals, the symptoms of poisonings are discussed to cows, sheep, donkeys, horses and chicks. Finally, the poisonous effects of cassava (Manihot esculenta) roots are summarised on experimental animals and on the human organism.
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PMID:Plant cyanogenic glycosides. 1066 9

Tonin(Persicae Semen) is the herb medicine that contains amygdalin as a major ingredient. Amygdalin in water is decomposed into benzaldehyde, HCN, and glucose by emulsin, a hydrolysis enzyme in tonin. A useful and practical method for the optimum extraction condition of amygdalin without enzymatic hydrolysis is required. The extraction yield of amygdalin of natural formula tonin was 0.1% from crude powders, 1.4% from small pieces, 3.5% from half pieces and 2.4% from whole pieces. The extraction yield of amygdalin of outer shell-eliminated tonin was 0.3% from crude powders, 1.4% from small pieces, and 3.5% from half pieces and whole pieces respectively. The extraction yield of amygdalin was most high when using the size larger than half.
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PMID:Development of quantitative extraction method of amygdalin without enzymatic hydrolysis from tonin(Persicae Semen) by high performance liquid chromatography. 1221 55

In macerates of black cherry (Prunus serotina Ehrh.) leaves and stems, (R)-prunasin is catabolized to HCN, benzaldehyde, and D-glucose by the sequential action of prunasin hydrolase (EC 3.2.1.21) and (R)-(+)-mandelonitrile lyase (EC 4.1.2.10). Immuno-cytochemical techniques have shown that within these organs prunasin hydrolase occurs within the vacuoles of phloem parenchyma cells. In arborescent leaves, mandelonitrile lyase was also located in phloem parenchyma vacuoles, but comparison of serial sections revealed that these two degradative enzymes are usually localized within different cells.
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PMID:Immunocytochemical Localization of Prunasin Hydrolase and Mandelonitrile Lyase in Stems and Leaves of Prunus serotina. 1223 9

Cyanogenesis (i.e. the evolution of HCN from damaged plant tissue) requires the presence of two biochemical pathways, one controlling synthesis of the cyanogenic glycoside and the other controlling the production of a specific degradative beta-glucosidase. The sole cyanogenic glycoside in Eucalyptus nobilis was identified as prunasin (D-mandelonitrile beta-D-glucoside) using HPLC and GC-MS. Seedlings from three populations of E. nobilis were grown under controlled conditions and 38% were found to be acyanogenic, a proportion far greater than reported for any other cyanogenic eucalypt. A detailed study of the acyanogenic progeny from a single open-pollinated parent found that 23% lacked a cyanogenic beta-glucosidase, 32% lacked prunasin and 9% lacked both. Of the remaining seedlings initially identified as acyanogenics, 27% contained either trace amounts of beta-glucosidase or prunasin, while 9% contained trace amounts of both. Results support the hypothesis that the two components necessary for cyanogenesis are inherited independently. Trace amounts are likely to result from the presence of non-specific beta-glucosidases or the glycosylation of the cyanohydrin intermediate by non-specific UDP glycosyl transferases.
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PMID:Cyanogenic Eucalyptus nobilis is polymorphic for both prunasin and specific beta-glucosidases. 1284 43

Cyanogenesis, the release of toxic HCN from damaged plant tissues, is generally considered as a constitutive plant defense. We found phenotypic plasticity of cyanogenesis in young leaves of lima bean Phaseolus lunatus based on increased activity of the beta-glucosidase in response to herbivore attack. Two aspects of plant cyanogenesis have to be considered in ecological analyses: (1) the cyanogenic potential (HCNp), which indicates the total amount of cyanide-containing compounds present in a given tissue, and (2) the cyanogenic capacity (HCNc), representing the release of HCN per unit time. This release is catalyzed by specific beta-glucosidases, whose activity is a crucial parameter determining overall toxicity. Enzymatic activity of beta-glucosidase-and, in consequence, the rate of HCN release-was increased significantly after 72 hr of incubation with spider mites as compared to non-infested leaves. Feeding by L1 larvae of Mexican bean beetles also led to enhanced enzymatic activity, whereas mechanical damage of leaf tissue had no effect on beta-glucosidase activity and the release of HCN. The results place plant cyanogenesis in the group of induced resistance traits, whose degree of activity depends on the feeding by a particular herbivore.
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PMID:Phenotypic plasticity of cyanogenesis in lima bean Phaseolus lunatus-activity and activation of beta-glucosidase. 1654 36

The tissue distributions of dhurrin [p-hydroxy-(S)-mandelonitrile-beta-d-glucoside] and of enzymes involved in its metabolism have been investigated in leaf blades of light-grown Sorghum bicolor seedlings. Enzymic digestion of these leaves using cellulase has enabled preparations of epidermal and mesophyll protoplasts and bundle sheath strands to be isolated with only minor cross-contamination. Dhurrin was located entirely in the epidermal layers of the leaf blade, whereas the two enzymes responsible for its catabolism, namely dhurrin beta-glucosidase and hydroxynitrile lyase, resided almost exclusively in the mesophyll tissue. The final enzyme of dhurrin biosynthesis, uridine diphosphate glucose:p-hydroxymandelonitrile glucosyltransferase, was found in both mesophyll (32% of the total activity of the leaf blade) and epidermal (68%) tissues. The bundle sheath strands did not contain significant amounts of dhurrin or of these enzymes. It was concluded that the separation of dhurrin and its catabolic enzymes in different tissues prevents its large scale hydrolysis under normal physiological conditions. The well documented production of HCN (cyanogenesis), which occurs rapidly on crushing Sorghum leaves, would be expected to proceed when the contents of the ruptured epidermal and mesophyll cells are allowed to mix.
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PMID:Tissue Distributions of Dhurrin and of Enzymes Involved in Its Metabolism in Leaves of Sorghum bicolor. 1666 Aug 50