The document discusses primary metabolism and the biosynthesis of primary metabolites in plants. It focuses on the shikimic acid pathway, which is a key intermediate step in the biosynthesis of aromatic amino acids and secondary metabolites derived from phenylalanine and tyrosine. The seven step shikimic acid pathway converts carbohydrate precursors into chorismate, which is then used to synthesize the aromatic amino acids phenylalanine, tyrosine, and tryptophan. This pathway is important for producing precursors for secondary metabolites in plants.

1. Biosynthesis of Primary Metabolites
• Living plants are solar-powered biochemical and biosyntheticlaboratory which manufactures
both primary and secondary metabolites from air, water, minerals and sunlight.
• The primary metabolites like sugars, amino acids & fatty acids thatare needed for general growth &
physiological development of plant which distributed in nature & also utilized as food by man.
• The secondary metabolites such as alkaloids, glycosides, Flavonoids, volatile oils etc are
biosynthetically derived fromprimary metabolites.
• Biosynthetic reactions are replica of common organic reactions like catalytic reactions,
phosphorylation, hydride transfer, oxidation, elimination, acylation, alkylation, reduction,
condensation,rearrangement etc.

2. Metabolism & Metabolic Pathways
o Cell Metabolism: Process by which living cell processnutrient molecule &livingstate.
o Metabolic Pathway: A complete set of chemical reactions that occur in living cells, allowing
cells to growand reproduce, maintain their structures, and respond totheir environments.
o Living cell require energy for biosynthesis, transport ofnutrient, motilityand maintenance.
o Energy is obtained from the catabolism of carboncompounds (carbohydrate)
o Carbohydrates are synthesized from CO2 and H2O in thepresent of light by photosynthesis.

3. ~ produce energy to the cell
~ requires energy
glucose to glycogen

4. Major Metabolic Pathways
●Cellular respiration:
Glycolysis
Anaerobic respiration
Kreb’s cycle / Citric acid cycle
Oxidative phosphorylation
● Creation of energetic compounds from non-living
matter:Photosynthesis (plants, algae cynobacteria)
Chemosynthesis (some bacteria)
Other pathways occurring in (most or) all living cell:
Fatty acid oxidation (β-oxidation)
Gluconeogenesis
HMG-CoA reductase pathway (isoprene prenylation)
Pentose phosphate pathway (hexose monophosphate)
Porphyrin synthesis (or heme synthesis) pathway
Urea cycle

5. Metabolites
●Metabolites are the intermediates & products of
metabolism.
●The term metabolite is usually restricted to small
molecules.
●A primary metabolite is directly involved in the
normal growth, development, and reproduction.
●A secondary metabolite is not directly involved
in those processes, but usually has important
ecological function.

6. Importance of photosynthesis in
formation of primary metabolites
● Photosynthesis is the process where plants convert sunlight into
energy, then store it as carbohydrates, sugars, such as glucose.
● Photosynthesis may be the most important process in ecosystems,
both brings in energy needed within the ecosystem, and
produce oxygen (O2) needed for cellular respiration, and the
production of more ATP.
● Photosynthesis has three basic steps:
1. Energy is captured from the sunlight.
2. Light energy is converted into chemical energy in the form of ATP
and NADPH.
3. Chemical energy is used to power the synthesis of organic
molecules (e.g. carbohydrates) from carbon dioxide (CO2).

7. Photosynthesis
● H2O + light + ADP + P ---> O2 + ATP + e-
● After the above steps occur in
photosystem II, the electron is finally sent
to photosystem I, where the following
happens.
● e- + NADP+
+ H ---> NADPH
● Now there are two high energy molecules,
fully charged and ready to be used. Plants
make more energy that it needs
immediately, so the NADPH and ATP are
used to make glucose as follows:
● CO2 + ATP + NADPH ---> C6H12O6
● This happens in Calvin cycle.

8. The primary and secondary metabolitesderived
from carbon metabolism

10. Difference between Primary and
secondary metabolites

11. Shikimic acid
●Commonly known as its anionic form shikimate, is a
cyclohexene, a cyclitol and a cyclohexanecarboxylic
acid.
●Its name comes from the Japanese flower shikimi the Japanese star
anise, Illiciumanisatum), from which it was first isolated in 1885 by
Johan Fredrik Eykman.
●The elucidation of its structure was made nearly 50 years later.
●Shikimic acid is also the glycoside part of some hydrolysable
tannins.

12. Shikimic Acid Pathway
●The Shikimic acid pathway is a key intermediate from carbohydrate for
the biosynthesis of C6-C3units (phenyl propane derivative).
●The Shikimic acid pathway converts simple carbohydrate precursors
derived from glycolysis and the pentose phosphate pathway to the
aromatic amino acids.
●The shikimate pathway is a 7 step metabolic route used by bacteria,
fungi, Algae, parasites, and plants for the biosynthesis of aromatic amino acids
(phenylalanine, tyrosine, and tryptophan).
●This pathway is not found in animals; therefore, phenylalanine and
tryptophan represent essential amino acids that must be obtained from the
animal's diet.
●Animals can synthesize tyrosine from phenylalanine, and therefore is not
an essential amino acid except for individuals unable to hydroxylate
phenylalanine to tyrosine).

14. ●Phosphoenolpyruvate and erythrose-4-phosphate react to form 2-keto3-
deoxy7phosphoglucoheptonic acid, in a reaction catalyzed by the enzyme
DAHP synthase.
●2-keto3-deoxy7phosphoglucoheptonic acid is then transformed to 3-
dehydroquinate (DHQ), in a reaction catalyzed by DHQ synthase.
●Although this reaction requires nicotinamide adenine dinucleotide
(NAD) as a cofactor, the enzymic mechanism regenerates it,
resulting in the net use of no NAD.

15. ●DHQ is dehydrated to 3-dehydroshikimic acid by the enzyme 3-dehydroquinate
dehydratase, which is reduced to shikimic acid by the enzyme shikimate dehydrogenase,
which uses nicotinamide adenine dinucleotide phosphate (NADPH) as a cofactor.
●The next enzyme involved is shikimate kinase, an enzyme that catalyzes the
ATPdependent phosphorylation of shikimate to form shikimate 3-phosphate.
Shikimate 3-phosphate is then coupled with phosphoenol pyruvate to give 5-
enolpyruvylshikimate-3-phosphate via the enzyme 5-enolpyruvylshikimate-3-
phosphate (EPSP) synthase.
●Then 5-enolpyruvylshikimate-3-phosphate is transformed into chorismate by
a chorismate synthase.

16. ●Prephenic acid is then synthesized by a Claisen rearrangement of chorismate
by Chorismate mutase.
Prephenate is oxidatively
decarboxylated with retention of
the hydroxyl group by
Prephenate dehydrogenase to
give phydroxyphenylpyruvate,
which is transaminated using
glutamate as the nitrogen
source to give tyrosine and α-
ketoglutarate.

17. P a t h w a y :
• Starting Point in The Biosynthesis of Some Phenolics Phenyl alanine and tyrosine are the precursors used in the
biosynthesis of phenylpropanoids.
o The phenylpropanoids are then used to produce the flavonoids, coumarins, tannins and
lignin.
o Gallic acid biosynthesis Gallic acid is formed from 3-dehydroshikimate bythe action of the enzyme shikimate
dehydrogenase to produce 3,5- didehydroshikimate.
o The latter compound spontaneously rearranges to gallic acid.
o Other compounds
o Shikimic acid is a precursor for:
o Indole, indole derivatives and aromatic amino acid tryptophan and tryptophan derivatives such as the
psychedelic compound dimethyltryptamine. & many alkaloids and other aromatic metabolites.

20. Uses:
●In the pharmaceutical industry, shikimic acid from the Chinese star
anise (Illicium verum) is used as a base material for production of
oseltamivir (Tamiflu).
●Target for drugs
●Shikimate can be used to synthesize (6S)-6-Fluoroshikimic acid, an
antibiotic which inhibits the aromatic biosynthetic pathway.
●Glyphosphate, the active ingredient in the herbicide
Roundup, kills plants by interfering with the shikimate
pathway in plants. More specifically, glyphosate inhibits the
enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS).
"Roundup Ready" genetically modified crops overcome that
inhibition.