A MOLECULAR AND BIOCHEMICAL-ANALYSIS OF THE STRUCTURE OF THE CYANOGENIC BETA-GLUCOSIDASE (LINAMARASE) FROM CASSAVA (MANIHOT-ESCULENTA CRANZ)

The cyanogenic β-glucosidase (linamarase) of cassava is responsible for the first step in the sequential breakdown of two related cyanoglucosides. Hydrolysis of these cyanoglucosides occurs following tissue damage and leads to the production of hydrocyanic acid. This mechanism is widely regarded as a defense mechanism against predation. A linamarase cDNA clone (pCAS5) was isolated from a cotyledon cDNA library using a white clover β-glucosidase heterologous probe. The nucleotide and derived amino acid sequence is reported and five putative N-asparagine glycosylation sites are identified. Concanavalin A affinity chromatography and endoglycosidase H digestion demonstrate that linamarase from cassava is glycosylated, having high-mannose-type N-asparagine-linked oligosaccharides. Consistent with this structure and the extracellular location of the active enzyme is the identification of an N-terminal signal peptide on the deduced amino acid sequence of pCAS5. © 1992.