The

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. A ...

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

catalyzes Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

the

chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

:''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, often forming a new double bond or a new ring structure. ...

s, specifically those carbon-oxygen lyases acting on phosphates. The systematic name 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 The terpenoids, also known as isoprenoids, are a class of naturally occurring organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeably with "terpenes", ...

In ''Stevia''

In ''

Stevia Stevia () is a natural sweetener and sugar substitute derived from the leaves of the plant species ''Stevia rebaudiana'', native to Paraguay and Brazil. The active compounds are steviol glycosides (mainly stevioside and rebaudioside), which h ...

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

biosynthesis Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. ...

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 toxicity. Both inhbit

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, the fir ...

of steviol glycoside 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