3-Deoxy--''arabino''-heptulosonic acid 7-phosphate (DAHP) is a 7-carbon ulosonic acid. This compound is found in the shikimic acid biosynthesis pathway and is an intermediate in the production of aromatic amino acids.

Phosphoenolpyruvate Phosphoenolpyruvate (2-phosphoenolpyruvate, PEP) is the carboxylic acid derived from the enol of pyruvate and a phosphate anion. It exists as an anion. PEP is an important intermediate in biochemistry. It has the high-energy phosphate, highest-e ...

and erythrose-4-phosphate react to form 3-deoxy--''arabino''-heptulosonate-7-phosphate (DAHP), in a reaction catalyzed by the enzyme

DAHP synthase 3-Deoxy-D-arabinoheptulosonate 7-phosphate (DAHP) synthase () is the first enzyme in a series of metabolic Chemical reaction, reactions known as the shikimate pathway, which is responsible for the biosynthesis of the amino acids phenylalanine, ...

. :

DAHP is then transformed to 3-dehydroquinate (DHQ), in a reaction catalyzed by

DHQ synthase The enzyme 3-dehydroquinate synthase (EC 4.2.3.4) catalyzes the chemical reaction : 3-deoxy-D-''arabino''-hept-2-ulosonate 7-phosphate \rightleftharpoons 3-dehydroquinate + phosphate The protein uses NAD+ to catalyze the reaction. This react ...

. Although this reaction requires

nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide (NAD) is a Cofactor (biochemistry), coenzyme central to metabolism. Found in all living cell (biology), cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphat ...

(NAD) as a cofactor, the enzymic mechanism regenerates it, resulting in the net use of no NAD. : Reaction catalyzed by 3-dehydroquinate synthase

The mechanism of

ring closure A cyclic compound (or ring compound) is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where ...

is complex, but involves an

aldol condensation An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties (of aldehydes or ketones) react to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), and this is then followed by dehydration t ...

at C-2 and C-7.

Metabolic engineering Metabolic engineering is the practice of optimizing genetic and regulatory processes within cells to increase the cell's production of a certain substance. These processes are chemical networks that use a series of biochemical reactions and enzy ...

has improved production of DAHP by ''

Escherichia coli ''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Escherichia'' that is commonly fo ...

''. The first step, condensation of 3-deoxy--''arabino''-heptulosonic acid 7-phosphate (DAHP) from PEP/E4P, uses three isoenzymes AroF, AroG, and AroH. Each one of these has its synthesis regulated from tyrosine, phenylalanine, and tryptophan, respectively. These isoenzymes all have the ability to help regulate synthesis of DAHP by the method of feedback inhibition. This acts in the cell by monitoring the concentrations of each of the three aromatic amino acids. When there is too much of any one of them, that one will allosterically control the DAHP synthetase by “turning it off”. With the first step of the common pathway shut off, synthesis of the three amino acids can not proceed. The rest of the enzymes is in the common pathway (conversion of DAHP to chorismate). : DAHP pathway

References

External links

* {{DEFAULTSORT:Deoxy-D-arabino-heptulosonic acid 7-phosphate, 3- Carboxylic acids Organophosphates Heptoses Monosaccharide derivatives