[1] SHIKIMIC ACID PATHWAY

Portion of a glycoside in charge of activity (active)

Non-sugar portion (aglycone/genin)

Portion of a glycoside in charge of solubility (non-active)

Sugar portion (glycone)

A very stable glycosidic bond that are not affected by simple hydrolysis

R-C-R

Enzyme that target only the beta forms of glycosides such as in bitter almonds

emulsin

Mineral acids used in the lab to separate glycone from aglycone units in a glycoside

Sulfuric acid and Hydrochloric acid

An enzyme commonly found in S groups of glycosides. For example, raw cabbage taste pungent because this enzyme is not hydroyzed (by cooking) yet.

myrosinase

Important pathways for aglycones

Mevalonate pathway and Shikimik acid pathway

A pathway that produces important secondary metabolites, including steroids such as saponins and cardiac glycosides

MVA pathway

A pathway that produces compounds such as phenols, flavonoids, even tannins, and various other glycosides.

Shikimic acid pathway

Formed during the Dark (Ligh-independent) reactions of photosynthesis

Glycone sugar

The backbone for many glycosides and volatile oils

phenylpropanoids

Which compounds condense (join together) at the start of shikimic acid pathway forming a 7C molecule?

Phosphoenolpyruvic acid (PEP) and Erythrose-4-phosphate (E4P)

What enzyme combines PEP and E4P (condensation)

DHAP synthase

What product is formed by the 7C molecule after cyclization-reduction?

3-Dehydroquinate (DHQ)

What enzyme catalyzes the cyclization of the 7C molecule?

DHQ synthase

What reaction occurs when DHQ converts 3-Dehydroquinate (DHQ) to 3-Dehydroshikimate (DHS)?

Dehydration

What enzyme catalyzes the formation of 3-Dehydroshikimate (DHS)?

DHQ dehydratase

What reaction occurs when DHS converts into Shikimic acid?

Reduction

What enzyme catalyzes the formation of Shikimic acid?

Shikimate dehydrogenase

What reaction occurs when Shikimic acid converts into Shikimic-3-phosphate?

Phosphorylation

What enzyme catalyzes the formation of Shikimate-3-phosphate?

Shikimate kinase

What product is formed when Shikimate-3-phosphate combines with PEP?

5-Enolpyruvylshikimate-3-phos phate (EPSP)

What enzyme catalyzes the formation of EPSP?

EPSP sythase

What is the product formed after the removal of phosphate and addition of PEP in Shikimate-3-phosphate?

Chorismic acid

What enzyme catalyzes the conversion of EPSP and the elimination of the 3-phosphate group to form Chorismic acid?

Chorismate synthase

What product is formed when chorismic acid is rearranged by chorsimate mutase?

Prephrenic acid

Precursor of anthranilic acid?

Chorismic acid

What intermediate compounds can be derived from anthranilic acid?

Indoles (e.g., vinblastine and vincristine)

What compounds combine to form tryptophan?

Indoles and serine

Precursor of Phenylalanine

phenyl-pyruvic acid

Precursor of Tyrosine

p-hydroxyphenyl-pyruvic acid

An enzyme that is not part of the “shikimate” loop, but is the most important enzyme for pharmacognosy. It sits at the exit of the pathway.

Phenylalanine Ammonia-Lyase (PAL)

Enzyme that strips the nitrogen (ammonia) off Phenylalanine to create Cinnamic Acid.

Phenylalanine Ammonia-Lyase (PAL)

This single reaction shifts the molecule from “Primary Metabolism” (making proteins) to “Secondary Metabolism” (making medicinal compounds).

Stripping the nitrogen from Phenylalanine to create cinnamic acid

Precursor of Gallic acid

Dehydroshikimic acid

Major building block of hydrolysable tannins

Gallic acid

What is the precursor for anthraquinones

Chorismic acid

Secondary metabolites that act as strong laxatives and cathartics. They have strong red or orange colors, so they were often used to produce dye in the past.

Anthraquinones

Products formed: from 3-Dehydroshikimic acid

Shikimic acid

Products formed: from Tryptophan

Indoles

Products formed: from Chorismic acid

Prephenic acid, Tryptophan, Anthraquinones

Products formed: from Prephenic acid

Phenylalanine, and Tyrosine and their derivatives.

Products formed: from Dehydroshikimic acid

Gallic acid

Products formed: from Phenylalanine

Cinnamic acid

Products formed: from Cinnamic acid

Coumarins (e.g., warfarin), Coumaric acid

Products formed: from Coumaric acid

Caffeic acid, Xanthones, Benzoquinones

Products formed: from Coniferyl alcohol dimers (monolignol)

Lignin

Products formed: from Ferulic acid

Vanillin

Products from coumaric acid that contributes to the flavor and aroma of plants

Caffeic acid and its derivatives (Xanthones in mangosteen and Benzoquinones)

A dimer of Coniferyl alcohol

Lignan

A polymer of Coniferyl alcohol

Lignin

Most important enzyme in the shikimic acid pathway that becomes the target of most herbicides?

EPSP synthase

What is the forking molecule to which aromatic acid will be produced by the plant?

Chorismic acid

Cinnamic acid backbone are _______

phenylpropanoids (C₆C₃)

Through __________, the phenylpropanoids (phenyl-pyruvic acid and p-Hydroxyphenyl-pyruvic acid) are converted to the twin aromatic amino acids, phenylalanine and tyrosine, respectively

reductive amination

_______ are single molecules created by union of two phenylpropanoid molecules (via oxidation)

Lignans

_______ are polymeric substance that assists cellulose in strengthening cell walls in wood. (responsible for secondary growth)

Lignins

Important LignAns: found in milk thistle, a hepatoprotectant (LiverAide^®)

Silymarin

Important LignAns: used as an anticancer drug (Warticon^®)

Podophyllotoxin

Lignan wax in leaves deposited in the epidermis of leaves

Cutin

Lignans found in the periderm or outer bark. Specifically in Phellem (cork tissue)

Suberin

Summary: Products from the Chorismate branch

Anthraquinones, Phenolic compounds, and Alcohol (salicylic acid)

Summary: Products from the Prephenic branch

Aldehydes (e.g., vanillin) , Lactone (e.g., coumarin), and Flavonoid

Summary: Products from the MVA Pathway

Saponins and Cardiac glycosides

Summary: Products from Other glycosides

Cyanophores and Glucosinolates