The

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 ...

''ent''-kaurene synthase (EC 4.2.3.19)

catalyzes Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

the

chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...

:''ent''-copalyl diphosphate

\rightleftharpoons

''ent''-kaurene + diphosphate This enzyme belongs to the family of

lyase In biochemistry, a lyase is an enzyme that catalyzes the breaking (an elimination reaction) of various chemical bonds by means other than hydrolysis (a substitution reaction) and oxidation Redox ( , , reduction–oxidation or oxidatio ...

s, specifically those carbon-oxygen lyases acting on phosphates. The

systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature. A semisystematic name or semitrivi ...

of this enzyme class is ''ent''-copalyl-diphosphate diphosphate-lyase (cyclizing, ''ent''-kaurene-forming). Other names in common use include ''ent''-kaurene synthase B, ''ent''-kaurene synthetase B, ''ent''-copalyl-diphosphate diphosphate-lyase, and (cyclizing). This enzyme participates in diterpenoid biosynthesis.

In ''Stevia''

In ''

Stevia Stevia () is a sweet sugar substitute that is about 50 to 300 times sweetness, sweeter than sugar. It is extracted from the leaves of ''Stevia rebaudiana'', a plant native to areas of Paraguay and Brazil. The active compounds in stevia are ...

'' spp., ''ent''-kaurene synthase is a required part of the

biosynthesis Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme-Catalysis, catalyzed processes where chemical substances absorbed as nutrients (or previously converted through biosynthe ...

steviol Steviol is a diterpene first isolated from the plant '' Stevia rebaudiana'' in 1931. Its chemical structure was not fully elucidated until 1960. Steviol occurs in the plant as steviol glycosides, sweet compounds that have found widespread use as ...

. Hajihashemi ''et al.'', 2013 find that it is involved in the drought stress response and because it mimics drought stress

paclobutrazol Paclobutrazol (PBZ) is the International Organization for Standardization, ISO trivial name, common name for an organic compound that is used as a Plant growth regulator, plant growth retardant and triazole fungicide. It is a known receptor antago ...

toxicity. Both inhibit transcription of

steviol glycoside Steviol glycosides are the chemical compounds responsible for the sweet taste of the leaves of the South American plant ''Stevia rebaudiana'' (Asteraceae) and the main ingredients (or chemical precursor, precursors) of many sugar substitute, swee ...

synthesis genes including ''ent''-kaurene synthase. This is believed to reduce steviol content in the final plant product.

References

* * * * EC 4.2.3 Enzymes of unknown structure {{4.2-enzyme-stub