Hydroxynitrile substrate acceptance

A new hydroxynitrile lyase (HNL) was isolated from the seed of Japanese apricot Prunus mume). It accepts benzaldehyde and a large number of unnatural substrates for the addition of HCN to produce the corresponding (7 )-cyanohydrins in excellent optical and chemical yields. A new high-performance liquid chromatography (HPLC)-based enantioselective assay technique was developed for the enzyme, which promotes the addition of KCN to benzaldehyde in a buffered solution (pH 4.0). Asymmetric synthesis of (7 )-cyanohydrins by a new HNL is described (Figure 8.4). ... 

We have found a new (/ )-hydroxynitrile lyase from Japanese apricot (P. mume). The new enzyme accepts a broad array of substrates, ranging from aromatic, heteroaromatic, bicyclic to aliphatic carbonyl compounds, and yields the corresponding cyanohydrins with excellent enantioselection. 

The nitrilase mediated DKR route to enantiomerically pure 2-hydroxycarboxylic acids is restricted to the (R)-enantiomers because, to our knowledge, no (S)-selec-tive nitrilases for cyanohydrin substrates are commonly available [11]. We reasoned that a fully enzymatic route to the (S)-acids should be possible by combining an (S)-selective oxynitrilase (hydroxynitrile lyase, EC 4.1.2.10, (S)-hydroxynitrile lyase) and a non-selective nitrilase in a bienzymatic cascade (see Figure 16.3). Besides being more environmentally acceptable than chemical hydrolysis, the mild reaction conditions of the combined enzymatic reaction would be compatible with a wide range of hydrolysable groups. 

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