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

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

found in many plants including

cassava ''Manihot esculenta'', common name, commonly called cassava, manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America, from Brazil, Paraguay and parts of the Andes. Although ...

and the butter bean. In cassava it is found in the

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

s. When the plant is chewed or ground, it exposes the enzyme to compounds like linamarin and lotaustralin which release

cyanide In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom. Ionic cyanides contain the cyanide anion . This a ...

compounds that can be lethal to the eater. In

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

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 ...

, which spontaneously decomposes to

hydrogen cyanide Hydrogen cyanide (formerly known as prussic acid) is a chemical compound with the chemical formula, formula HCN and structural formula . It is a highly toxic and flammable liquid that boiling, boils slightly above room temperature, at . HCN is ...

(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 An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

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