Lyases mandelonitrile lyase

MANDELONITRILE LYASE MANDELONITRILE LYASE Manganese(ll) carbonate (MnCOj), SOLUBILITY RRODUCT Manganese(ll) hydroxide (Mn(OH)2), SOLUBILITY RRODUCT Manganese ion,... 

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]. 

Kuroki, G.W. and Conn, E.E. (1989) Mandelonitrile lyase fromXimenia americana L. stereospecificity and lack of flavin prosthetic group. Proceedings of the National Academy of Sciences of the United States of America, 86, 6978-6981. 

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. 

Also in the (R)-class of Hnls, although of more limited application, is the (R)-mandelonitrile lyase from Phlebodium aureum [35] which catalyses the addition to some aromatic and heterocyclic carbonyls but only poorly to aliphatic carbonyls. 

This enzyme [EC 4.1.2.10], also known as hydroxynitrile lyase and (i )-oxynitrilase, catalyzes the conversion of mandelonitrile to cyanide and benzaldehyde. 

Fig. 2.2.3.S Preferred substrates of Sf HNL. 4-Hydroxy-mandelonitrile and tyrosyl-arginine are the preferred substrates of the main hydroxynitrile lyase activity and the carboxypeptidase side-activity. Since both substrates resemble the aromatic ring of tyrosine, catalysis at the same active site can be assumed.

Hydroxynitrile lyase Synthesis of (R)-mandelonitrile in sodium phosphate buffer/methyl tert-butyl ether [70]... 

The first synthesis of mandelonitrile using hydroxynitrile lyases was published by Rosenthaler in 1908 [7], but only fifty years later this research field regained attention for synthetic purposes by Becker et al. [8-10]. However, because of the spontaneous chemical addition of HCN in the aqueous and alcoholic medium used, only low enantiomeric excesses ( ) were achieved. In addition, the low solubility of many substrates in the buffer made this reaction unsuitable for laboratory scale and industrial application. 

For the synthesis of cyanohydrins nature provides the chemist with R- and S-selective enzymes, the hydroxynitrile lyases (HNL) [4-7]. These HNLs are also known as oxynitrilases and their natural function is to catalyze the release of HCN from natural cyanohydrins like mandelonitrile and acetone cyanohydrin. This is a defense reaction of many plants. It occurs if a predator injures the plant cell. The reaction also takes place when we eat almonds. Ironically the benzaldhyde released together with the HCN from the almonds is actually the flavor that attracts us to eat them. 

Cheng, l.R. and Roulton, J.E. (1993) Cloning of cDNA of Prunus serotina (R)-(-l-)mandelonitrile lyase and identification of a putative FAD-binding site. Plant Cell Physiol, 34,1139-43. 

Hu, Z. and Poulton, J.E. (1997) Sequencing, genomic organization and preliminary promoter analysis of black cherry (R)-(+)-mandelonitrile lyase gene. Plant Physiol, 115(4), 1359-69. 

Wajant, H., Roerster, S., Selmar, D., Effenberger, R. and Pfizenmaier, K. (1995) Purification and characterization of a novel (R)-mandelonitrile lyase from the fern Phlebodium aureum. Plant Physiol, 109,1231-8. 

E. Wehtje, E Adlercreutz, and B. Mathiasson, Formation of C—C bonds by mandelonitrile lyase in organic solvents. Biotech. Bioeng., 36 39 (1990). 

Generally, low intensity ultrasound can increase the activity of enzymes and immobilized enzymes, or can improve the metabolism of cells by the improvement of mass transfer to substrates. One example is the enzymatic decomposition of mandelonitrile by mandelonitrile lyase in di-isopropyl ether which has been accelerated 10-fold by ultrasound [66], The mandelonitrile lyase was not denatured by 30 kHz operating at 0.5 W cm-2 and pulsed at 15 s per min. 

Examples of LLC phases for enzyme stabilization and bio catalysis include the micellar and LLC phases water (or glucose in water)/oclanol/octyl-/3-D-glucoside LLC system for accelerating /3-D-glucosidase-calalyzed hydrolysis of octyl-/ -n-glucoside to form glucose and octanol [108] and the use of LLC phases of numerous commercial surfactants to accelerate the (S)-hydroxynitrile lyase-catalyzed synthesis of (S)-mandelonitrile [109]. 

Nippon Shokubai Kagaku Kogyo disclosed a complementary process for the synthesis of optically active cyanohydrins. (S)-hydroxynitrile lyase derived from plants like Euphorbiaceae, Gramineae, and Olacaceae could successfully be applied to synthesize 99.9% optically active (S)-mandelonitrile (S)-175 [147]. The enzymes showed high absorption ratios when immobilized on porous inorganic material such as ceramics, silica, alumina, or silica/alumina zeolithes and were also used for the synthesis of other cyanohydrins. 

Alcohol oxidase P-Glucosidase and mandelonitrile lyase Rhamnosidase... 

EC4. Lyases enzymes cleaving C-C, C-O, C-N, and other bonds by other means than by hydrolysis or oxidation. They differ from other enzymes in that two substrates are involved in one reaction direction, but only one in the other direction. Example mandelonitrile lyase (EC 4.1.2.10)... 

Gross, M., G. H. Jacobs, and J. E. Poulton, A rapid and sensitive spectrophotometric assay for prunasin hydrolase activity employing purified mandelonitrile lyase, Anal. Biochem., 119, 25-30 (1982). 

Lyases Addition to double bonds C=C, C=N, C=0, etc. (C=0) aldolases mandelonitrile lyase (C=C) aspartase fumarase... 

There are many examples of nitrilase-catalyzed reactions in which amides form a considerable amount of the reaction products, such as the transformations of acrylonitrile analogs and a-fluoroarylacetonitriles by nitrilase 1 from Arabidopsis thaliana [17], the conversion of p-cyano-L-alanine into a mixture of L-asparagine and L-aspartic acid by nitrilase 4 from the same organism [18] or the transformations of mandelonitrile by nitrilase from Pseudomonas jhiorescens [19] or some fungi [8], Moreover, formamide is the only product of the cyanide transformation by cyanide hydratase. Therefore, this enzyme was classified as a lyase (EC 4.2.1.66), although it is closely related to nitrilases, as far as its aa sequence and reaction mechanism are concerned [3]. 

Through the years, several names and abbreviations for HNLs have been used, e.g., emulsin (for extracts from defatted almond meal), oxynitiilase, mandelonitrile lyase, MDL, MNL, and acetone cyanohydrin lyase, all with different prefixes like D, l, (R), (5), (+), (—), or a. Throughout this chapter, the designation hydroxynitrile lyase, abbreviated as HNL and the prefixes R and S, will be used. 

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