Seeds of rosary pea, Abrus precatorius : A novel source of hydroxynitrile lyase

Seeds of Abrus precatorius (rosary pea) were identified as a new and potential source of hydroxynitrile lyase. Hydroxynitrile lyase from the seeds of this plant was purified up to 9 fold with specific activity of 577 Umg-1 protein by using ion exchange and gel filtration chromatographic techniques. The purified enzyme was a heteromer with estimated native molecular mass 205 kDa and its subunits showed two bands of molecular mass of 42.0 and 36.5 kDa in SDS-PAGE, respectively. The enzyme exhibited maximum activity at 30ºC with 0.1 M sodium citrate buffer (pH 5). It has KM of 13 mM and Vmax of 625 Umg-1 of protein with mandelonitrile as a substrate. In 120 ml of reaction mixture containing 25 ml of benzaldehyde (substrate) and 6.75 mg of purified enzyme produced 17.5 g of mandelonitrile.