Exploring hydroxynitrile lyase activity in seed sources and characterisation of a novel hydroxynitrile lyase from Pyrus communis (Pear)

Abstract

The study aimed to explore hydroxynitrile lyase (HNL) activity in locally available plant seeds, addressing the gap between the extensive number of cyanogenic plants and the relatively few documented HNLs. Our research delves into the Hydroxynitrile Lyase (HNL) activity in the seeds of twenty plants, unearthing three novel sources of HNL: Caesalpinia crista, Pinus roxburghii, and Pyrus communis. The latter, Pyrus communis, exhibited the highest HNL activity (3.57 μmol/min/mg), sparking further investigation into its enzyme extraction and reaction conditions. The optimal conditions for extracting crude Pyrus communis HNL from the defatted meal were found to be 8 % meal, extraction pH 7.0 and soaking for 8 h. For reaction condition optimisation, the enzyme displayed the highest activity in citrate buffer at pH 5.0. The ideal temperature for the enzyme reaction was 30 °C, with an incubation time of 30 min (7.59 μmol/min/mg). The optimal concentration of the racemic mixture of mandelonitrile for maximum activity was 10 mM, resulting in a maximum activity of 8.79 μmol/min/mg. The qualitative HPLC showed the presence of mandelonitrile peak at ∼RT 4.29 min synthesized using Pyrus communis HNL. The study highlights the potential of Pyrus communis HNL for developing new bioprocess to synthesize chiral cyanohydrins.