Metabolic pathways in higher plants and their determination
a) Brief study of basic metabolic pathways and formation of different secondary metabolites through these pathways- Shikimic acid pathway
shikimate pathway (shikimic acid pathway) is a seven-step metabolic pathway used by bacteria, archaea, fungi, algae, some protozoans, and plants for the biosynthesis of folates and aromatic amino acids (tryptophan, phenylalanine, and tyrosine). This pathway is not found in animal cells.
The important intermediate product formed in this pathway is called shikimic acid, hence the name shikimic acid pathway.
Shikimic acid is named after the highly toxic Japanese shikimi (Illicium anisatum) flower from which it was first isolated . This biochemical pathway is a major link between primary and secondary metabolism in higher plants.
In plants, these aromatic amino acids are not only crucial components of protein biosynthesis; they also serve as precursors for diverse secondary metabolites that are important for plant growth. These secondary metabolites are called phenolic compounds and are synthesized when needed by the plant.
The shikimate pathway consists of seven sequential enzymatic steps and begins with an aldol-type condensation of two phosphorylated active compounds, the phosphoenolpyruvic acid (PEP), from the glycolytic pathway, and the carbohydrate D-erythrose-4-phosphate, from the pentose phosphate cycle, to give 3-deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP).
The important 7 steps reactions Substrates, enzymes and product
1). Phosphoenolpyruvate (PEP), erythrose-4-phosphate======= 3-Deoxy-D-arabino-heptulosonate-7-phosphate synthase DAHPS/Co2+, Mg2+ or Mn2+ =========== 3-Deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP), Pi
2). 3-Deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP)=======
3-Dehydroquinate synthase DHQS (EC. 4.2.3.4)/Co2+, NAD===========
3-Dehydroquinic acid (DHQ), Pi
3). 3-Dehydroquinic acid (DHQ)=======
3-Dehydroquinate dehydratase (DHQ dehydratase==========
3-Dehydroshikimic acid (DHS), H2O
4). 3-Dehydroshikimic acid (DHS), NADPH + H+=============
Shikimate dehydrogenase ===========
Shikimic acid, NADP+
5). Shikimic acid, ATP===========
Shikimate kinase enzyme ============
Shikimic acid 3-phosphate
6). Shikimic acid 3-phosphate (S3P), PEP==================
5-Enolpyruvylshikimate 3-phosphate synthase, also called aroA enzyme
===================
5-Enolpyruvylshikimate 3-phosphate
7). 5-Enolpyruvylshikimate 3-phosphate (EPSP)=================
Chorismate synthase=====
========
Chorismic acid, Pi
.jpeg)
The importance and role of Shikimic acid pathway:~
biosynthesis of folates and aromatic amino acids (phenylalanine, tyrosine, and tryptophan).
it is also an intermediate in production of tannins, flavones, coumarins and vanillin.
Phenyl alanine and tyrosine are the precursors used in the biosynthesis of phenylpropanoids. The phenylpropanoids are then used to produce the flavonoids, coumarins, tannins and lignin.
Shikimic acid is a precursor for indole, indole derivatives and aromatic amino acid tryptophan and tryptophan derivatives such as the psychedelic compound dimethyltryptamine. many alkaloids and other aromatic metabolites
.jpeg)