Cyanogenic glucosidases

Figure 1. 6-Glucosidase-mediated hydrolysis of cyclopentenoid cyanogenic glycosides.

Ballhorn, D. J., Hell, M. and Lieberei, R. 2006. Phenotypic plasticity of cyanogen-esis in lima bean Phaseolus lunatus - Activity and activation of beta-glucosidase. Journal of Chemical Ecology, 32(2) 261-275. 

We have previously developed a protein homology model based on the sequence of aphid myrosinase and templates from plant myrosinase and cyanogenic P-glucosidase.12 These enzymes all adopt the (p/a)8-barrel structure typical of this... 

The myrosinase-glucosinolate system occurs in 16 plant families.17 It is likely that this system evolved from the ancient (and near ubiquitous) cyanogenic glycosides. This hypothesis is supported by the similarity, in sequence and structure, of glucosinolate biosynthetic enzymes and the hydrolytic enzymes (myrosinase or p-glucosidase).18 The biochemistry of these metabolites also indicates a convincing evolutionary relationship.19 Furthermore, on the basis of robust phylogenetic trees,... 

Keywords cyanogenic glycosides glucosinolates non-protein amino acids cytochrome P450 cyanogenesis fj-glucosidase myrosinase mustard oil... 

In the first step, cyanogenic glucosides are cleaved by p-glucosidases. The resulting a-hydroxynitriles are unstable and dissociate to produce a carbonyl compound and HCN. In many plants, the dissociation of the cyanohydrins is accelerated by an HNL. In plants that accumulate diglucosidic compounds, the hydrolysis of these substances can be achieved by either a sequential or a simultaneous mechanism (Kuroki et al, 1984) (Fig. 3.5). 

Cyanogenesis is initiated following the hydrolysis of cyanogenic glucosides by 3-glucosidases, which are often referred to as cyanogenic 3-glucosidases. Such enz)mies are localized in the apoplasm, in protein bodies or in... 

Table 3.2 Substrate specificity and localization of cyanogenic j6-glucosidases...

In contrast to the high homologies found among the cyanogenic (3-glucosidases, the situation is completely different for the hydroxynitrile lyasses isolated from various plants. The enzyme from Sorghum, which does... 

Barrett, T., Suresh, C.G., Tolley, S.P., Sodson, E.J. and Hughes, M.A. (1995) The crystal structure of cyanogenic p-glucosidase from white clover, a family 1-glycosyl hydrolase. Structure, 3, 951-1000. 

Hosel, W., Tobler, L., Eklund, S.H. and Conn, E.E. (1987) Characterization of fj-glucosidases with high specificity for the cyanogenic glucoside, dhurrtn, in Sorghum bicolor (L.). Moench seedlings. Arch. Biochem. Biophys., 252,152-62. 

Hughes, M. A., Brown, K., Pancoro, A., Murray, B.S., Oxtoby, E. and Hughes, J. (1992) A molecular and biochemical analysis of the structure of the cyanogenic fj-glucosidase (linamarase) from cassava (Manihot esculenta Cranz). Arch. Biochem. Biophys., 295, 273-9. 

Nahrstedt, A., Hosel, W. and Walter, A. (1979) Characterization of cyanogenic glucosides and fj-glucosidases in Triglochin maritima seedlings. Phytochemistry, 18, 1137-41. 

Oxtoby, E., Dunn, M.A., Pancoro, A. and Hughes, M. A. (1991) Nucleotide and derived amino acid sequence of the cyanogenic p-glucosidase (linamarase) from white clover (Trifolium repens L.). Plant Mol. Biol, 17, 209-20. 

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