3-Deoxy--''arabino''-heptulosonic acid 7-phosphate (DAHP) is a 7-carbon ulonic acid. This compound is found in the shikimic acid biosynthesis pathway and is an intermediate in the production of aromatic amino acids. Phosphoenolpyruvate and erythrose-4-phosphate react to form 3-deoxy--''arabino''-heptulosonate-7-phosphate (DAHP), in a reaction catalyzed by the enzyme DAHP synthase. : DAHP synthase reaction

DAHP is then transformed to

3-dehydroquinate 3-Dehydroquinic acid (DHQ) is the first carbocyclic intermediate of the shikimate pathway. It is created from 3-deoxyarabinoheptulosonate 7-phosphate, a 7-carbon ulonic acid, by the enzyme DHQ synthase. The mechanism of ring closure is complex, ...

(DHQ), in a reaction catalyzed by

DHQ synthase DHQ may refer to: * 3-Dehydroquinic acid, the first carbocyclic intermediate of the shikimate pathway * Digital Humanities Quarterly ''Digital Humanities Quarterly'' is a peer-reviewed open-access academic journal covering all aspects of digital m ...

. Although this reaction requires

nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an aden ...

(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 al ...

is complex, but involves an aldol condensation 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''. 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