5-enolpyruvylshikimate-3-phosphate (EPSP) synthase 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. A ...

produced by plants and

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s. EPSPS

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 ...

: : phosphoenolpyruvate (PEP) + 3-phospho

shikimate Shikimic acid, more commonly known as its anionic form shikimate, is a cyclohexene, a cyclitol and a cyclohexanecarboxylic acid. It is an important biochemical metabolite in plants and microorganisms. Its name comes from the Japanese flower ''sh ...

(S3P) phosphate + 5-enolpyruvylshikimate-3-phosphate (EPSP) Thus, the two substrates of this

are phosphoenolpyruvate (PEP) and 3-phosphoshikimate, whereas its two products are

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phospho ...

and 5-enolpyruvylshikimate-3-phosphate. This enzyme is not present in animals. It presents an attractive biological target for

herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

s, such as glyphosate. A glyphosate-resistant version of this gene has been used in

genetically modified crops Genetically modified crops (GM crops) are plants used in agriculture, the DNA of which has been modified using genetic engineering methods. Plant genomes can be engineered by physical methods or by use of ''Agrobacterium'' for the delivery of ...

Nomenclature

The enzyme belongs to the family of

transferase A transferase is any one of a class of enzymes that catalyse the transfer of specific functional groups (e.g. a methyl or glycosyl group) from one molecule (called the donor) to another (called the acceptor). They are involved in hundreds of di ...

s, to be specific those transferring

aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used as ...

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloalk ...

groups other than

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...

groups. The systematic name of this enzyme class is phosphoenolpyruvate:3-phosphoshikimate 5-''O''-(1-carboxyvinyl)-transferase. Other names in common use include: * 5-enolpyruvylshikimate-3-phosphate synthase, * 3-enolpyruvylshikimate 5-phosphate synthase, * 3-enolpyruvylshikimic acid-5-phosphate synthetase, * 5′-enolpyruvylshikimate-3-phosphate synthase, * 5-enolpyruvyl-3-phosphoshikimate synthase, * 5-enolpyruvylshikimate-3-phosphate synthetase, * 5-enolpyruvylshikimate-3-phosphoric acid synthase, * enolpyruvylshikimate phosphate synthase, and * 3-phosphoshikimate 1-carboxyvinyl transferase.

Structure

EPSP synthase is a monomeric enzyme with a molecular mass of about 46,000. It is composed of two domains, which are joined by protein strands. This strand acts as a hinge, and can bring the two protein domains closer together. When a substrate binds to the enzyme, ligand bonding causes the two parts of the enzyme to clamp down around the substrate in the active site. EPSP synthase has been divided into two groups according to glyphosate sensitivity. Class I enzyme, contained in plants and in some bacteria, is inhibited at low micromolar glyphosate concentrations, whereas class II enzyme, found in other bacteria, is resistant to inhibition by glyphosate.

Shikimate pathway

EPSP synthase participates in the biosynthesis of the

aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...

amino acids

phenylalanine Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino a ...

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Gr ...

, and

tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α- carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic ...

via the shikimate pathway in bacteria, fungi, and plants. EPSP synthase is produced only by plants and micro-organisms; the gene coding for it is not in the mammalian

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...

Gut flora Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut mi ...

of some animals contain EPSPS.

Reaction

EPSP synthase catalyzes the reaction which converts shikimate-3-phosphate plus phosphoenolpyruvate to 5-enolpyruvylshikimate-3-phosphate (EPSP) by way of an acetal-like

tetrahedral intermediate A tetrahedral intermediate is a reaction intermediate in which the bond arrangement around an initially double-bonded carbon atom has been transformed from trigonal to tetrahedral. Tetrahedral intermediates result from nucleophilic addition to a c ...

. Basic and

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

s in the

active site In biology and biochemistry, the active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction. The active site consists of amino acid residues that form temporary bonds with the substrate (binding site) a ...

are involved in

deprotonation Deprotonation (or dehydronation) is the removal (transfer) of a proton (or hydron, or hydrogen cation), (H+) from a Brønsted–Lowry acid in an acid–base reaction.Henry Jakubowski, Biochemistry Online Chapter 2A3, https://employees.csbsju.ed ...

of the

hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy g ...

of PEP and in the proton-exchange steps related to the tetrahedral intermediate itself, respectively. EPSPreactionII

Studies of the enzyme kinetics for this reaction have determined the specific sequence and energetics of each step of the process.

Herbicide target

EPSP synthase is the biological target for the herbicide glyphosate. Glyphosate is a competitive inhibitor of EPSP synthase, acting as a transition state analog that binds more tightly to the EPSPS-S3P complex than PEP and inhibits the shikimate pathway. This binding leads to inhibition of the enzyme's catalysis and shuts down the pathway. Eventually this results in organism death from lack of aromatic amino acids the organism requires to survive. A version of the enzyme that both was resistant to glyphosate and that was still efficient enough to drive adequate plant growth was identified by Monsanto scientists after much trial and error in an ''

Agrobacterium ''Agrobacterium'' is a genus of Gram-negative bacteria established by H. J. Conn that uses horizontal gene transfer to cause tumors in plants. ''Agrobacterium tumefaciens'' is the most commonly studied species in this genus. ''Agrobacterium'' is ...

'' strain called CP4 (). The strain CP4 was found surviving in a waste-fed column at a glyphosate production facility. The CP4 EPSP synthase enzyme has been engineered into several

Nomenclature

Structure

Shikimate pathway

Reaction

Herbicide target

References

Further reading