enzymology 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 ...

, an anthranilate phosphoribosyltransferase () 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 ...

that

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, ...

:anthranilate + phosphoribosyl pyrophosphate

\rightleftharpoons

N-(5-phosphoribosyl)-anthranilate + diphosphate The two substrates of this enzyme are

anthranilate Anthranilic acid is an aromatic acid with the formula C6H4(NH2)(CO2H) and has a sweetish taste. The molecule consists of a benzene ring, ''ortho''-substituted with a carboxylic acid and an amine. As a result of containing both acidic and basic f ...

and

phosphoribosyl pyrophosphate Phosphoribosyl pyrophosphate (PRPP) is a Sugar phosphates, pentose phosphate. It is a biochemical intermediate in the formation of purine nucleotides via Inosinic acid, inosine-5-monophosphate, as well as in pyrimidine nucleotide formation. Hence ...

. Its two

products Product may refer to: Business * Product (business), an item that can be offered to a market to satisfy the desire or need of a customer. * Product (project management), a deliverable or set of deliverables that contribute to a business solution ...

are N-(5-phosphoribosyl)-anthranilate and diphosphate. This enzyme participates in aromatic amino acid

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 ...

and two-component system (general).

Nomenclature

This enzyme belongs to the family of

glycosyltransferase Glycosyltransferases (GTFs, Gtfs) are enzymes ( EC 2.4) that establish natural glycosidic linkages. They catalyze the transfer of saccharide moieties from an activated nucleotide sugar (also known as the "glycosyl donor") to a nucleophilic gl ...

s, specifically the pentosyltransferases. 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 N-(5-phospho-D-ribosyl)-anthranilate:diphosphate phospho-alpha-D-ribosyltransferase. Other names in common use are: * anthranilate 5-phosphoribosylpyrophosphate * anthranilate phosphoribosylpyrophosphate phosphoribosyltransferase * anthranilate-PP-ribose-P phosphoribosyltransferase * phosphoribosyl-anthranilate pyrophosphorylase * phosphoribosylanthranilate pyrophosphorylase * phosphoribosylanthranilate transferase * phosphoribosyltransferase * PRT

Function

Anthranilate phosphoribosyltransferase (AnPRT) is a

transferase In biochemistry, 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 ...

enzyme which catalyses one of the most fundamental biochemical reactions: the transfer of a ribose group between an aromatic base and

phosphate Phosphates are the naturally occurring form of the element phosphorus. 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 orthop ...

groups. More specifically, AnPRT facilitates the formation of a carbon-nitrogen bond between 5-phospho-alpha-D-ribose 1-diphosphate (PRPP) and anthranilate.

Reaction

In the aromatic amino acid biosynthesis pathway specifically the

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 aromat ...

synthesis portion, AnPRT draws anthranilate and 5-phospho-alpha-D-ribose 1-diphosphate into the active site of the protein. Through the

Sn1 The unimolecular nucleophilic substitution (SN1) reaction is a substitution reaction in organic chemistry. The Hughes-Ingold symbol of the mechanism expresses two properties—"SN" stands for "nucleophilic substitution", and the "1" says that t ...

mechanism below, AnPRT transfers the 5-phospho-alpha-D-ribose group (shown in blue) to the anthranilate (shown in red) from the diphosphate molecule (shown in black). AnPRT catalyzed rxn 1

Structure

As of late 2007, 12

structures A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

have been solved for this class of enzymes, with PDB accession codes , , , , , , , , , , , and . AnPRT has four

domain A domain is a geographic area controlled by a single person or organization. Domain may also refer to: Law and human geography * Demesne, in English common law and other Medieval European contexts, lands directly managed by their holder rather ...

s and its

quaternary structure Protein quaternary structure is the fourth (and highest) classification level of protein structure. Protein quaternary structure refers to the structure of proteins which are themselves composed of two or more smaller protein chains (also refe ...

consists of two identical protein structures. Each domain of AnPRT contains a magnesium ion and a pyrophosphate molecule as 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, the ''binding s ...

. The secondary structure of AnPRT consists mainly of

alpha helices An alpha helix (or α-helix) is a sequence of amino acids in a protein that are twisted into a coil (a helix). The alpha helix is the most common structural arrangement in the secondary structure of proteins. It is also the most extreme type of l ...

with a

beta sheet The beta sheet (β-sheet, also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a gene ...

within each domain.

Homologues

There are homologues of AnPRT within ''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...

'', ''

Kluyveromyces lactis ''Kluyveromyces lactis'' is a ''Kluyveromyces'' yeast commonly used for genetic studies and industrial applications. Its name comes from the ability to assimilate lactose and convert it into lactic acid. ''Kluyveromyces lactis'' (formerly ''Sac ...

'', ''

Schizosaccharomyces pombe ''Schizosaccharomyces pombe'', also called "fission yeast", is a species of yeast used in traditional brewing and as a model organism in molecular and cell biology. It is a unicellular eukaryote, whose cells are rod-shaped. Cells typically meas ...

'', ''

Magnaporthe grisea ''Magnaporthe grisea'', also known as rice blast fungus, rice rotten neck, rice seedling blight, blast of rice, oval leaf spot of graminea, pitting disease, ryegrass blast, Johnson spot, neck blast, wheat blast and , is a plant-pathogenic fungus ...

'', ''

Neurospora crassa ''Neurospora crassa'' is a type of red bread mold of the phylum Ascomycota. The genus name, meaning 'nerve spore' in Greek, refers to the characteristic striations on the spores. The first published account of this fungus was from an infestatio ...

'', ''

Arabidopsis thaliana ''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally ...

'', and ''

Oryza sativa ''Oryza sativa'', having the common name Asian cultivated rice, is the much more common of the two rice species cultivated as a cereal, the other species being ''Oryza glaberrima, O. glaberrima'', African rice. It was History of rice cultivation ...

''. All of these organisms are alike in the sense that they make all of the amino acids needed for proper protein formation (also called

autotrophs An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms. Autotrophs produce complex organic compounds (such as carbohydrates, fats, and proteins) us ...

). AnPRT is vital in these organisms because it is a vital step in the pathway to synthesis tryptophan, an

essential amino acid An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. Of the 21 amino acids common to all life forms ...

in humans, which humans take from eating plants or fungi.

Mutations in AnPRT

(This entire section comes from the paper written by Dr. Robert Last and his collaborators, referenced here:Last, R.L, Li, J, & Rose, A.B. (January, 1997). An allelic series of blue fluorescent trpl mutants of arabidopsis thaliana. Genetics Society of America, (145), 197-205.) An experiment was conducted on the varying mutations in the gene which codes for AnPRT in Arabidopsis. This study focused on the observed fluorescence of Arabidopsis plants when the gene which coded for AnPRT was mutated. It was found that there were nine mutations of the gene all with varying

auxotrophic Auxotrophy ( "to increase"; ''τροφή'' "nourishment") is the inability of an organism to synthesize a particular organic compound required for its growth (as defined by IUPAC). An auxotroph is an organism that displays this characteristic; ''a ...

and prototrophic capabilities. It was discovered that there was an increased level of anthranilate in the cells of Arabidopsis which were mutated. This was concluded to be linked to the fluorescence of the plants. This study's relevance comes from the applications of the conclusions found by the scientists. The auxotrophic mutant could be used as a

selectable marker A selectable marker is a gene introduced into cell (biology), cells, especially bacteria or cells in cell culture, culture, which confers one or more traits suitable for artificial selection. They are a type of reporter gene used in laboratory micr ...

in plant

transformation Transformation may refer to: Science and mathematics In biology and medicine * Metamorphosis, the biological process of changing physical form after birth or hatching * Malignant transformation, the process of cells becoming cancerous * Trans ...

s. This can lead to a better way to engineer plants and find new ways to develop their systems to work for humanities purposes.

References

{{Portal bar, Biology, border=no EC 2.4.2 Enzymes of known structure Anthranilates