ACETONE CYANOHYDRIN LYASE FROM MANIHOT-ESCULENTA (CASSAVA) IS SEROLOGICALLY DISTINCT FROM OTHER HYDROXYNITRILE LYASES

A non-flavoprotein hydroxynitrile lyase clearly different from other h ydroxynitrile lyases was isolated from Manihot esculenta (cassava) by combined application of anion exchange chromatography and gel filtrati on. The purified protein was resolved, upon SDS-PAGE, as a single band of 30 kDa, while the molecular mass of the native enzyme, determined by gel filtration on Superdex 200 was 124 kDa. Diisopropyl fluorophosp hate and phenylmethanesulfonyl fluoride inhibited the activity of acet one cyanohydrin lyase, indicating an enzymatically important serine re sidue. Using immunological techniques, we demonstrate that there is no serological relationship between acetone cyanohydrin lyase from cassa va and various other hydroxynitrile lyases. This supports the idea tha t hydroxynitrile lyases have independently evolved from various ancest oral proteins. The hydroxynitrile lyase from cassava is capable of cat alyzing the addition of HCN to several aliphatic carbonyls in organic media, demonstrating the potential usefulness of this enzyme in stereo selective synthesis of aliphatic cyanohydrins, which are important bui lding blocks in organic synthesis.