A hydroxynitrile lyase

Crystallisation studies using the PaHnl have also been reported [50]. Four isomeric forms of this Hnl were isolated from the aforementioned defatted almond meal and subsequently separated. Three of these isoenzymes were successfully crystallised and shown to belong to the monoclinic space group. Though by this means additional data were included, the clearest picture for the 3D structure of a hydroxynitrile lyase still remains with the HbHnl. 

Hughes, J., de Carvalho, F.J.P and Hughes, M.A. (1994) Purification, characterization and cloning of a-hydroxynitrile lyase from cassava (Manihot esculenta Crantz). Ardz. 

Selmar, D., Lieberei, R., Biehl, B. and Conn, E.E. (1989) a-Hydroxynitrile lyase in Hevea brasiliensis and its significance for rapid cyanogenesis. Physiol. Plantarum, 75, 97-101. 

Oxynitrilases or hydroxynitrile lyases (HNL) constitute a group of enzymes that catalyze the reversible addition of HCN to ketones and aldehydes. The natural role of these enzymes is a defence mechanism of higher plants against herbivores, whereby HCN is liberated from cyanoglucosides such as prunasin (almond, cherry, apple) by the action of a glycosidase and a hydroxynitrile lyase. 

Enantiomerically pure cyanohydrins can easily be modified chemically or enzymatically (Scheme 4.12B), providing access to chiral a-hydroxy acids, a-hydroxy amides, 2-aminoalcohols, and epoxides. Replacement of the hydroxyl functionahty by a better leaving group, such as a sulfonyl moiety (e.g. tosylate), allows the introduction of various other nucleophiles with inversion at the stereocenter [51a]. The structures of some bioactive molecules that have been synthesized using a biotransformation step with a hydroxynitrile lyase are depicted in Scheme 4.12B [51a, 52]. 

These two methods involve the potential release of toxic HCN during the reaction and a cleaner as well as a safer method is to use acetone cyanohydrin 128 as a cyanide transfer reagent. The enzyme from the Brazilian rubber tree Hevea brasiliensis, called a hydroxynitrile lyase, catalyses cyanohydrin formation from aliphatic as well as aromatic aldehydes.40... 

Muller, E. and A. Nahrstedt, Purification and characterization of an a-hydroxynitrile lyase from the haemolymph of the larvae of Zygaena trifolii, Planta Medica, 56, 611-612 (1990). 

Like the benzoxazinones, cyanogenic glucosides belong to the preformed defense of the plant and are stored in the vacuole. Upon disruption of the plant tissue, they are degraded by P"glucosidases to the corresponding a-hydrox-ynitriles, which are hydrolyzed by a-hydroxynitrile lyases to aldehydes or ketones and toxic hydrogen cyanide (HCN) (Fig. 13). Since the a-hydroxynitriles are unstable, they can also... 

As shown in Fig. 16.4, P-glucosidase hydrolysis produces an unstable hydroxynitrile which slowly degrades into the corresponding carbonyl compound and HCN. However, most legume seeds contain a hydroxynitrile lyase which accelerates this reaction. 

Griengl reported the first example of hydroxynitrile lyase-catalyzed cyanohydrin formation in a mixed solvent system of [bmim][BF4] and buffer (pH 3.7) (1 1) (Fig. 19). In the reaction, a mixed solvent system was essential, but excellent results were obtained. 

Starting from enantiomerically pure 4-methylsulfanyl-mandelonitrile, thiamphenicol and florfenicol have been enantioselectively synthesized (Figure 5.14). The enantiomerically pure 4-methylsulfanyl-mandelonitrile was obtained by hydrocyanation reaction of 4-methy lsulfany 1-benzaldehyde catalyzed by (M)-hydroxynitrile lyase of Badamu (almond from Xinjiang, China) (Prunus communis L. var. dulcis Borkh), which, after an extensive screening, was found to be a highly effective bio-catalyst for this reaction [85]. 

Dreveny, I., Gruber, K., Glieder, A. et al. (2001) The hydroxynitrile lyase from almond a lyase that looks like an oxidoreductase. Structure (London, England 1993), 9, 803-815. 

Dreveny, I., Kratky, C. and Gruber, K. (2002) The active site of hydroxynitrile lyase from Prunus amygdalus modeling studies provide new insights into the mechanism of cyanogenesis. Protein Science A Publication of the Protein Society, 11, 292-300. 

Zuegg, J., Gruber, K., Gugganig, M. et al. (1999) Three-dimensional structures of enzyme-substrate complexes of the hydroxynitrile lyase from Hevea brasiliensis. Protein Science A Publication of the Protein Society, 8, 1990-2000. 

Lauble, H., Miehlich, B., Forster, S. et al. (2002) Crystal structure of hydroxynitrile lyase from Sorghum bicolor in complex with the inhibitor benzoic acid a novel cyanogenic enzyme. Biochemistry, 41, 12043-12050. 

Andexer, J., von Langermann, J., Mell, A. et al. (2007) An R-selective hydroxynitrile lyase from Arabidopsis thaliana with an alpha/beta-hydrolase fold. Angewandte Chemie-International Edition, 46, 8679-8681. 

Hernandez, L., Luna, H., Rulz-Teran, F. and Vazquez, A. (2004) Screening for hydroxynitrile lyase activity in crude preparations of some edible plants. Journal of Molecular Catalysis B-Enzymatic, 30, 105-108. 

Glieder, A., Weis, R., Skranc, W. et al. (2003) Comprehensive step-by-step engineering of an (R)-hydroxynitrile lyase for large-scale asymmetric synthesis. Angewandte Chemie-International Edition, 42, 4815 4818. 

Andexer, J., Guterl, J.-K., Pohl, M. and Eggert, T. (2006) A high-throughput screening assay for hydroxynitrile lyase activity. Chemical Communications, 4201 4203. 

Krammer, B., Rumbold, K., Tschemmernegg, M. et al. (2007) A novel screening assay for hydroxynitrile lyases suitable for high-throughput screening. Journal of Biotechnology, 129, 151-161. 

Willeman, W.F., Straathof, A.J.J. and Heijnen, J.J. (2002) Reaction temperature optimization procedure for the synthesis of (/ )-mandelonitrile by Primus amygdalus hydroxynitrile lyase using a process model approach. Enzyme and Microbial Technology, 30, 200-208. 

Hickel, A., Radke, C.J. and Blanch, H.W. (1999) Hydroxynitrile lyase at the diisopropyl ether/water interface evidence for interfacial enzyme activity. Biotechnology and Bioengineering, 65, 425—136. 

Veum, L., Hanefeld, U. and Pierre, A. (2004) The first encapsulation of hydroxynitrile lyase from Hevea brasiliensis in a sol-gel matrix. Tetrahedron, 60, 10419-10425. 

Purkarthofer, T., Gruber, K., Gruber-Khadjawi, M,et al. (2006) A biocatalytic Henry reaction - the hydroxynitrile lyase from Hevea brasiliensis also catalyzes nitroaldol reactions. Angewandte Chemie (International Edition in English), 45, 3454-3456. 

Rhodococcus erythropolis NCIMB 11540 has been employed as biocatalyst for the conversion of (R)- or (.S )-cyanohydrins to the corresponding (R)- or (S)-a-hydroxycarboxylic acids with an optical purity of up to >99% enatiomeric excess (ee) [27-29] the chiral cyanohydrins can separately be produced using hydroxynitrile lyase from Hevea braziliensis or from Prunus anygdalis [30]. Using the combined NHase-amidase enzyme system of the Rhodococcus erythropolis NCIMB 11 540, the chiral cyanohydrins were first hydrolyzed to the... 

The hydroxynitrile lyase (HNL)-catalysed cyanohydrin reaction is a useful method to synthesize enantiopure a-hydroxy nitriles and the corresponding a-hydroxy acids. However, small ketones, such as 2-butanone, are converted with low selectivities, due to the poor discrimination between methyl and ethyl. ... 

F6rster,S., Roos, J., Effenberger, E., Wajant, H. and Sprauer, A. Liber die erste rekombinante Hydroxynitril-Lyase und ihre Anwendung in der Synthese von (5)-Cyanhydrinen. Angew. Chem., 1996,108, 493. 

The production of optically active cyanohydrins, with nitrile and alcohol functional groups that can each be readily derivatized, is an increasingly significant organic synthesis method. Hydroxynitrile lyase (HNL) enzymes have been shown to be very effective biocatalysts for the formation of these compounds from a variety of aldehyde and aliphatic ketone starting materials.Recent work has also expanded the application of HNLs to the asymmetric production of cyanohydrins from aromatic ketones. In particular, commercially available preparations of these enzymes have been utilized for high ee (5)-cyanohydrin synthesis from phenylacetones with a variety of different aromatic substitutions (Figure 8.1). 

Chiral cyanohydrins are versatile intermediates in the synthesis of a-hydroxy acids, /3-amino alcohols, amino nitriles, a-hydroxy ketones and aziridines. For the synthesis of enantiopure cyanohydrins, the use of hydroxynitrile lyases is currently the most effective approach.Application of an organic-solvent-free system allows thermodynamically hindered substrates to be converted with moderate to excellent yields. With the use of the highly selective hydroxynitrile lyase from Manihot esculenta, the syntheses of several acetophenone cyanohydrins with excellent enantioselectivities were developed (Figure 8.2). (5)-Acetophenone cyanohydrin was synthesized on a preparative scale. ... 

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