The Purification and Properties of a Uridine Diphosphate Glucose: Aldehyde Cyanohydrin β-Glucosyltransferase from Sorghum Seedlings

A UDP-glucose:aldehyde cyanohydrin β-glucosyltransferase has been isolated and partially purified from shoots of etiolated seedlings of Sorghum bicolor (Linn) Moench. The enzyme catalyzes the formation of dhurrin (p-hydroxy(S)-mandelonitrile-β-d-glucopyranoside), the cyanogenic glucoside of sorghum, from UDP-glucose and (R,S)-p-hydroxymandelonitrile. The reaction with (R,S)-p-hydroxymandelonitrile is stereospecific for the (S) enantiomer since only dhurrin, and not a mixture of dhurrin and its epimer taxiphyllin, was formed. Although the enzyme exhibited higher activity with aromatic cyanohydrins, it also accepted other aromatic substrates.