Hydroxynitrile lyase from Sorghum bicolor : a glycoprotein heterotetramer

Abstract Highly purified hydroxynitrile lyase from Sorghum bicolor L. (EC 4.1.2.11) is composed of two different subunits, α and β. The structure of the active enzyme is 2α2β. It was shown in an immunoblot assay that both subunits are glycoproteins. The nature of the carbohydrate residues was further investigated by means of biotin-labeled lectins. The influence of glycosylation on the mobility of hydroxynitrile lyase in SDS-PAGE was demonstrated with enzymatically deglycosylated protein. Enzyme assays with hydroxynitrile lyase, which was partially deglycosylated at reversible denaturing conditions, suggested that the sugar residues are necessary for the protein to maintain its functional structure.