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Shikimic acid Pathway:- Hand Written Notes


Erythrose-4-phosphate and phosphoenol pyruvate interact each other and synthesize the 2-keto-3-deoxy-7-phosphoglucoheptonic acid and enzyme which mediate this reaction is DAPH synthase.
• DHQ (dehyroquinate) synthase catalyse the further reaction and form the 3-dehydroquinate from the 2- keto-3-deoxy-7-phosphoglucoheptonic acid.
• NADC (Nicotinamide adenine dinucleotide) used as a cofactor in this reaction Production of primary and secondary metabolites in Plants
• In the presence of another enzyme 3-dehydroquinate dehydratase the DHQ remove the water and form 3-dhydroshikimic acid.
• ATP base phosphorylation occurs of the product dehydroshikimic acid and form the shikimate- 3- phosphate in the presence of enzyme shikimate kinase. Phosphoenol pyruvate reacts with this shikimate- 7- phosphate to form 5-enol pyruvyl shikimate-3- phosphate with the help of enzyme 5-enol pyruvyl shikimate-3-phosphate (EPSP) synthase.
• The next product chorismate is formed from the product 5-enol pyruvyl shikimate-3 phosphate via the enzyme chorismate synthase.
• Clasien rearrangement reaction occurs with chorismate in the presence of enzymes chorismate mutase and prephenic acid was formed.
• From chorismic acid various intermediate product like Anthranillic acid, phosphoribosyl anthranillic acid were formed which will last produce tryptophan.
• While prephenic acid converted into phenyl pyruvic acid or 4-hydroxy phenyl pyruvic acid which in last produce the amino acid phenyl alanine or tyrosine.
Production of Amino acids by Shikimic acid pathway
Shikimic acid pathway leading to the biosynthesis of diverse bioactive principles
Biosynthesis of Glycosides:
The metabolic process of glycoside formation occurs in two steps. In first step various types of aglycone are formed by biosynthetic reactions whereas in second step coupling of
aglycone with sugar moiety occurs. In different types of glycsides interaction of nucleotide glycoside occurs between UDP-glucose with alcoholic or phenolic group of secondary compound aglycone (called O-glycosides), through linkage with carbon (C-glycosides),
nitrogen (N-glycosides) or sulphur (S-glycosides).
The following two steps are involved in this process:
1. In first step, the uridine triphosphate (UTP) transferred an uridylyl group to sugar-1-
phosphate and forms UDP-sugar and inorganic pyrophosphate. The enzyme which
catalyzes this reaction is uridylyl transferases.
Uridylyl transferases
UTP + Sugar-1-PO4 UDP- sugar + PP1
2. In second step, transfer of the sugar moiety from UDP to a suitable acceptor (aglycone) occurs. This reaction is mediated by enzyme glycosyl transferases and forms glycoside.
Glycosyl transferases
UDP-sugar + Acceptor (aglycone) Acceptor-sugar (glycoside) + UDP
The sugars of glycosides are monosaccharides (like Rhamnose, Glucose, Frucose or deoxy sugars i.e. digitoxose or cymarose).
The aglycone moieties of cardiac glycosides are steroidal in nature. These are derivatives of cyclopentenophenanthrene ring which contains unsaturated lactone ring attached with
C17, a 14-alpha hydroxyl group and a cisjucture of ring C and D.
The anthraquinone glycosides are biosynthesized from shikimic acid pathway in Rubiaceae family. The alizarin biosynthesis shows ring A is derived from shikimic acid whereas mevalonic acid is included in ring C.