Unit 1 of Pharmacognosy and phytochemistry II V semester Third year pharmacy

1. Amino acid pathway
Prepared By,
Mrs.Kulkarni D.M.
Assistant Professor,
Yash Institute of Pharmacy,
Aurangabd

2. Amino acids
Amino acids are organic compounds containing
amine(-NH2) and carboxyl (-COOH) functional groups,
along with a side chain (R) group specific to each
amino acid.
Many amino acids contain only carbon, hydrogen,
oxygen and nitrogen, but other atoms may be present
(e.g. sulphur in cystine, and iodine in thyroxin).
As already mentioned, more than one amino group
may be present (e.g. Lysine, diaminocaproic acid) and
more than one carboxylic acid group (e.g. aspartic or
amino succinic acid). Some amino acids are aromatics
such as phenylalanine, or heterocyclic

3. Amino acid pathway:
Plants and bacteria can synthesize all 20 of the
amino acids.
Humans cannot synthesize 9 of them.
These 9 amino acids must come from our diets and are
called essential amino acids.
They are Histidine, Isoleucine, Leucine, Lysine, Methionine,
Phenylalanine, Threonine, Tryptophan, and Valine.
The 11 amino acids are called non-essential amino acids
Alanine, Arginine, Aspargine, Aspartate, Cysteine,
Glutamate, Glutamine, Glycine, Proline, Serine and
Tyrosine.
The non-essential amino acids are synthesized by simple
pathways.
Biosynthesis of the essential amino acids are complex.
All 3 aromatic amino acids are derived from shikimate
pathway

4. All amino acids are derived from intermediates in
glycolysis, the citric acid cycle, or pentose phosphate
pathway.
Nitrogen enters these pathways by way of glutamate
and glutamine.
Organisms vary greatly in their ability to synthesize the
20 common amino acids.
Whereas most bacteria and plants can synthesize all 20,
mammals can synthesize about half of them- generally
those with simple pathways: the non-essential amino
acids not needed in the diet.
The remainder, the essential amino acids must be
obtained from food

5. Amino acids are required for many vital functions of an
organism.
Mammals can either synthesize amino acids from
common keto acid carbon skeletons and preformed
amino nitrogen such as that of glutamate or obtain
them from their diets.
The biosynthesis of nonessential amino acids involves
relatively simple pathways, whereas those forming the
essential amino acids are generally more complex.
The amino acid biosynthetic pathways are subject to
allosteric end- product inhibition; the regulatory enzyme
is usually the first in the sequence. Regulation of the
various synthetic pathways is coordinated.
Some important genetic diseases associated with
amino acid metabolism include phenylketonuria,
albinism, homocystinuria, alkaptonuria, and maple syrup
urine disease.

6. Amino acid synthesis is the set of biochemical processes
(metabolic pathways) by which the amino acids are
produced. The substrates for these processes are
various compounds in the organism's diet or growth
media. Not all organisms are able to synthesize all
amino acids. For example, humans can only synthesize
11 of the 20 standard amino acids (a.k.a. non-essential
amino acid), and in time of accelerated growth,
histidine can be considered an essential amino acid.

7. Of the basic set of twenty amino acids (not counting
selenocysteine), humans cannot synthesize
eight. In addition, the amino acids arginine, cysteine,
glycine, glutamine, histidine, proline, serine, and
tyrosine are considered conditionally essential,
meaning they are not normally required in the diet
but must be supplied exogenously to specific
populations that do not synthesize it in adequate
amounts.

8. For example, enough arginine is synthesized by the urea cycle to
meet the needs of an adult but perhaps not those of a growing
child. Amino acids that must be obtained from the diet are called
essential amino acids. Nonessential amino acids are produced in
the body. The pathways for the synthesis of nonessential amino
acids are quite simple. Glutamate dehydrogenase catalyzes the
reductive amination of α-ketoglutarate to glutamate. A
transamination reaction takes place in the synthesis of most
amino acids. At this step, the

9. chirality of the amino acid is established.
Alanine and aspartate are synthesized by the transamination of
pyruvate and oxaloacetate, respectively.
Glutamine is synthesized from NH4+ and glutamate, and asparagine
is synthesized similarly.
Proline and arginine are derived from glutamate. Serine, formed
from 3-phosphoglycerate, is the precursor of glycine and cysteine.
Tyrosine is synthesized by the hydroxylation of phenylalanine, an
essential amino acid.
The pathways for the biosynthesis of essential amino acids are much
more complex than those for the nonessential ones.

10. Amino acid pathway

11. Alkaloids derived from ornithine