OIA2007 W4 SHIKIMIC ACID PATHWAY

Primary Metabolites

Widely distributed

Concentrated in seed & storage organs

Low value high bulk commodity items of plant

Required for general growth & development

Secondary Metabolites

Derived from primary metabolites (biosynthetically)

Limited in distribution & in specific families

Not necessary for growth & development, but for pollination attracants, environmental adaptation, or protection

Origin of Shikimic Acid Pathway

**Memorise diagram

Convert glucose to different size (no. of C) sugar by acyl interchanges

Amino Acids synthesised are precursor materials for secondary metabolites

Shikimic Acid Formation

Chorismic Acid (key intermediate) : Use to form different acids

****Shikimic Acid -> Chorismic Acid -> Anthranilic acid -> Tryptophan -> Alkaloids [MAIN PATHWAY]

Complete Pathway:

Phosphoenolpyruvate (PEP) + Erythrose-4-phosphate [condensation] -> 2-keto, 3-deoxy, 7-phospho, D-glucoheptonic acid [cyclization] -> 3-dehydro quinic acid [dehydration] -> 3-dehydro Shikimic Acid [NADPH] -> Shikimic Acid [ATP] -> Phosphorylated Shikimic Acid + pyruvic acid (from PEP hydrolysis) [Nucleophilic Addition to C=O] -> [dehydration] -> [remove phosphoric acid] -> Chorismic Acid -> Anthranilic acid -> Tryptophan -> Alkaloids (End Product)

Detail Steps:

Phosphoenolpyruvate (PEP) + Erythrose-4-phosphate (E4P) [condensation]: PEP remove phosphate group by add H2O (form phosphoric acid) -> form C=O, E4P add H+ at C=O, PEP combine at C-1 of E4P

2-keto, 3-deoxy, 7-phospho, D-glucoheptonic acid [cyclization]: remove phosphate group

3-dehydro quinic acid [dehydration]: remove H2O at C-1 form C=C

3-dehydro Shikimic Acid [NADPH]: add NADPH (C=O form C-OH)

Shikimic Acid [ATP]: C-OH (C3) form C-OP

Pyruvic acid [Nucleophilic Addition to C=O]: Phosphorylated Shikimic Acid combine at C=O of pyruvic acid

Remove H2O, remove phosphoric acid -> Chorismic Acid -> Anthranilic acid -> Tryptophan -> Alkaloids

Other products involved different pathways (not Shikimic Acid Pathway)

Prephenic Acid (from Chorismic Acid)

Chorismic Acid in pseudoaxial conformation undergo Claisen Type rearrangement to form Prephenic Acid. Prephenic Acid convert to phenylpyruvic acid by undergoing decarboxylation & dehydration, which undergo Transamination to form phenylalanine. Prephenic Acid convert to 4-hydroxyphenylpyruvic acid by undergoing decarboxylation, which undergo Transamination to form tyrosine.

Phenylalanine & Tyrosine (common source)

Prephenic Acid -> phenylalanine

Prephenic Acid -> tyrosine

Sufficient tyrosine w/o convert phenylalanine to tyrosine

Shikimic Acid Pathway (plants)

Form aromatic amino acid -> Tryptophan, phenylalanine & tyrosine, building block for alkaloids and flavonoids

Phenylpropanoids (phenyl C-3)

Cleave at C3 side chain -> many phenyl-C1