Linamarase, or beta-D-glucosidase (), is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

found in many plants including

cassava ''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America. Although a perennial plant, cassava is extensively cultivated ...

and the butter bean. In cassava it is found in the cell walls. When the plant is chewed or ground, it exposes the enzyme to compounds like

linamarin Linamarin is a cyanogenic glucoside found in the leaves and roots of plants such as cassava, lima beans, and flax. It is a glucoside of acetone cyanohydrin. Upon exposure to enzymes and gut flora in the human intestine, linamarin and its methylat ...

and

lotaustralin Lotaustralin is a cyanogenic glucoside found in small amounts in Fabaceae austral trefoil (''Lotus australis''), cassava (''Manihot esculenta''), lima bean (''Phaseolus lunatus''), roseroot (''Rhodiola rosea'') and white clover (''Trifolium repen ...

which release

cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...

compounds that can be lethal to the eater. In

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

s, chronic toxicity is more likely than death. This action of the enzyme is used by many cultures to process cassava into an edible substance. The enzyme converts the cyanide containing compounds into

acetone cyanohydrin Acetone cyanohydrin (ACH) is an organic compound used in the production of methyl methacrylate, the monomer of the transparent plastic polymethyl methacrylate (PMMA), also known as acrylic. It liberates hydrogen cyanide easily, so it is used as a s ...

, which spontaneously decomposes to hydrogen cyanide (HCN). The HCN then either dissolves readily in water or is released into the air. Not all cyanide can be removed during processing. Linamarase can be inhibited by low pH via a dilute acid.

References

T. Itoh-Nashida, M. Hiraiwa and Y. Uda 1987. "Purification and properties of beta-D-glucosidase (linamarase) from the butter bean, Phaseolus lunatus".
Last accessed 13 November 2005.
Heuberger, Christoph. 10 May 2005. "Physicochemical properties of cassava tubers with focus on cyanide content in fermented products".
Last accessed 13 November 2005. EC 3.2.1 Enzymes {{3.2-enzyme-stub