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

A non-flavoprotein hydroxynitrile lyase clearly different from other hydroxynitrile lyases was isolated from Manihot esculenta (cassava) by combined application of anion exchange chromatography and gel filtration. 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 fluorophosphate and phenylmethanesulfonyl fluoride inhibited the activity of acetone cyanohydrin lyase, indicating an enzymatically important serine residue. Using immunological techniques, we demonstrate that there is no serological relationship between acetone cyanohydrin lyase from cassava and various other hydroxynitrile lyases. This supports the idea that hydroxynitrile lyases have independently evolved from various ancestoral proteins. The hydroxynitrile lyase from cassava is capable of catalyzing the addition of HCN to several aliphatic carbonyls in organic media, demonstrating the potential usefulness of this enzyme in stereoselective synthesis of aliphatic cyanohydrins, which are important building blocks in organic synthesis.