SHIKIMIC ACID

'Shikimic acid'
Chemical structure of shikimic acid 3D model of shikimic acid
Chemical name	(3''R'',4''S'',5''R'')-3,4,5-Trihydroxy- 1-cyclohexenecarboxylic acid
Chemical formula	C7H10O5
Molecular mass	174.15 g/mol
Melting point	185–187 °C
CAS number	[138-59-0]
InChI	InChI=1/C7H10O5/c8-4- 1-3(7(11)12)2-5(9)6(4) 10/h1,4-6,8-10H,2H2, (H,11,12)/t4-,5-,6- /m1/s1/f/h11H
EINECS number	205-334-2

'Shikimic acid', more commonly known as its anionic form 'shikimate', is an important biochemical intermediate in plants and microorganisms. Its name comes from the Japanese flower ''shikimi'' (シキミ, ''Illicium anisatum''), from which it was first isolated.
Shikimic acid is a precursor for:

★ the aromatic amino acids phenylalanine and tyrosine,

★ indole, indole derivatives and aromatic amino acid tryptophan,

★ many alkaloids and other aromatic metabolites,

★ tannins, flavonoids, and lignin.
In the pharmaceutical industry, shikimic acid from the Chinese star anise is used as a base material for production of Tamiflu (oseltamivir). Although shikimic acid is present in most autotrophic organisms, it is a biosynthetic intermediate and generally found in very low concentrations. The low isolation yield of shikimic acid from the Chinese star anise is blamed for the 2005 shortage of oseltamivir. Shikimic acid can also be extracted from the seeds of the sweetgum fruit, which is abundant in North America, in yields of around 1.5%, so just 4 kg of sweetgum seeds are enough for fourteen packages of Tamiflu. By comparison star anise has been reported to yield 3 to 7% shikimic acid. Recently biosynthetic pathways in ''E. coli'' have been enhanced to allow the organism to accumulate enough material to be used commercially.^[1]

Contents

Biosynthesis

References

External links

Biosynthesis

Phosphoenolpyruvate and erythrose-4-phosphate react to form 3-deoxy-D-arabinoheptulosonate-7-phosphate (DAHP), in a reaction catalysed by the enzyme DAHP synthase. DAHP is then transformed to 3-dehydroquinate(DHQ), in a reaction catalysed by DHQ synthase. Although this reaction requires NAD as a cofactor, the enzymic mechanism regenerates it, resulting in the net use of no NAD (note diagram is incorrect).

DHQ is dehydrated to 3-dehydroshikimate by the enzyme dehydroquinase, which is reduced by to shikimic acid by the enzyme shikimate dehydrogenase, which uses NADPH as a cofactor.

References

1. Star role for bacteria in controlling flu pandemic?, , David, Bradley, Nature Reviews Drug Discovery,

External links

★ Shikimate and chorismate biosynthesis