Screening for new hydroxynitrilases from plants.

Area of Science:

• Biocatalysis and Enzyme Discovery
• Plant Biochemistry
• Analytical Chemistry

Background:

• Chiral cyanohydrins are valuable synthetic intermediates.
• Hydroxynitrile lyases (HNLs) catalyze cyanohydrin formation stereoselectively.
• Plant-derived HNLs offer potential for green chemistry applications.

Purpose of the Study:

• To develop a simple HPLC method for determining HNL activity and stereochemistry.
• To screen a diverse range of plant species for novel (R)- and (S)-HNL activities.
• To characterize the substrate specificity of identified plant HNLs.

Main Methods:

• Development of a high-performance liquid chromatography (HPLC) method for chiral mandelonitrile analysis.
• Screening of 163 plant species (74 families) for hydroxynitrile lyase (HNL) activity.
• Partial purification and characterization of active HNL enzymes.

Main Results:

• A simple HPLC method was established for assessing HNL activity and stereochemistry.
• Screening identified (S)-HNL activity in Baliospermum montanum leaves.
• (R)-HNL activity was found in Passiflora edulis, Eriobotrya japonica, Chaenomles sinensis, Sorbus aucuparia, Prunus mume, and Prunus persica.
• Partially purified (R)-HNLs from P. edulis and E. japonica showed activity on both benzaldehyde and aliphatic ketones.
• High enantiomeric excess (ee) was achieved for (R)-mandelonitrile (85.0%) and (R)-methylpropylketone cyanohydrin (87.0%).

Conclusions:

• The developed HPLC method is effective for screening plant HNLs.
• Several plant species possess valuable (R)- and (S)-HNL activities.
• Plant-derived HNLs demonstrate potential as biocatalysts for synthesizing chiral cyanohydrins with high enantioselectivity.