Amino acids are the building blocks of proteins, playing a crucial role in various biological processes. They are categorized into essential and non-essential amino acids based on the body's ability to synthesize them. While essential amino acids must be obtained through the diet, non-essential amino acids can be synthesized by the body. General Pathway of Amino Acid Biosynthesis: Amino acid biosynthesis involves complex metabolic pathways that differ for each amino acid. However, a general overview can be provided: Carbon Skeleton Formation: Amino acids are composed of a central carbon atom (alpha carbon) bonded to a hydrogen atom, an amino group (NH2), a carboxyl group (COOH), and a side chain (R group) specific to each amino acid. The carbon skeletons of amino acids are derived from intermediates of glycolysis, citric acid cycle, and pentose phosphate pathway. Transamination: A crucial step in amino acid biosynthesis is the transamination reaction, where an amino group is transferred from an amino acid donor to an alpha-keto acid acceptor. This reaction is catalyzed by aminotransferases or transaminases, and pyridoxal phosphate (PLP) acts as a cofactor. Specific Pathways for Essential Amino Acids: Essential amino acids, which cannot be synthesized de novo by the body, have specific biosynthetic pathways. For example, lysine and methionine biosynthesis involve the aspartate family pathway, while valine, leucine, and isoleucine biosynthesis occur through the branched-chain amino acid (BCAA) pathway. Non-Essential Amino Acid Biosynthesis: Non-essential amino acids can be synthesized by the body through various pathways. For instance, glutamate serves as a precursor for the synthesis of several amino acids, including proline, arginine, and ornithine. Specific Amino Acid Biosynthesis Pathways: Serine and Glycine Biosynthesis: Serine is derived from 3-phosphoglycerate and can be converted to glycine. The enzyme serine hydroxymethyltransferase plays a key role in interconverting serine and glycine. Histidine Biosynthesis: Histidine biosynthesis involves a unique pathway that starts with phosphoribosyl pyrophosphate (PRPP) and includes several enzymatic steps. Tyrosine and Phenylalanine Biosynthesis: The shikimate pathway is essential for the biosynthesis of aromatic amino acids, including tyrosine and phenylalanine. Chorismate is a key intermediate in this pathway. Arginine Biosynthesis: Arginine biosynthesis involves the urea cycle and the ornithine biosynthetic pathway. Citrulline serves as a key intermediate in these processes. Proline Biosynthesis: Proline is derived from glutamate through a two-step reduction process involving pyrroline-5-carboxylate (P5C). Regulation of Amino Acid Biosynthesis: Amino acid biosynthesis is tightly regulated to maintain a balance between the body's requirements and energy conservation. Feedback inhibition and genetic regulation play key roles in controlling the activity of enzymes involved in these p

1. Biosynthesis of Amino Acids

2. • Biosynthesis of amino acids is a
crucial process in living
organisms, involving the
production of amino acids from
simple compounds.
• It plays a fundamental role in
the overall metabolism of cells
and is essential for various
biological processes.

3. General Biosynthetic Pathways
1 Precursors
Amino acid biosynthesis utilizes various precursors derived from
central metabolic pathways, such as the citric acid cycle and
glycolysis. These pathways provide the necessary building blocks
for amino acid synthesis.
2 Importance
The central metabolic pathways play a crucial role by supplying
key intermediates required for amino acid biosynthesis, ensuring a
balanced and harmonious cellular metabolism.
3 Connection
A close connection between amino acid biosynthesis and central
metabolic pathways ensures the integration and efficient utilization
of resources within the cell.

4. Role of Enzymes in Amino Acid
Biosynthesis
1 Enzyme Specificity
Each step in the biosynthesis
pathway involves specific
enzymes that catalyze the
transformation of substrates
into amino acids.
2 Regulation of Enzymes
Enzyme activity is tightly
regulated to maintain
optimal levels of different
amino acids in the cell.

5. Biosynthesis of Amino Acids
• The carbon skeletons of many amino acids
may be derived from metabolites in central
pathways, allowing the biosynthesis of
some, but not all, the amino acids in humans.
• Amino acids that can be synthesized in this
way are therefore not required in the diet
(nonessential amino acids)

6. • The amino acids having carbon skeletons
that cannot be derived from normal human
metabolism must be supplied in the diet
(essential amino acids)
• For the biosynthesis of non-essential amino
acids, amino groups must be added to the
appropriate carbon skeletons
• This generally occurs through the
transamination of an α-keto acid
corresponding to that specific amino acid.

8. Amino Acid Biosynthetic families, grouped by metabolic
precursors

9. • Amino acids precursors are
intermediates in glycolysis, the
citric acid cycle, or the pentose
phosphate pathway.
• Histidine comes from Ribose 5-
phosphate that is product of
pentose phosphate pathway.
• Serine comes from 3-
phosphoglycerate and from
serine we can make more amino
acids like glycine and cysteine.
• Tryptophan, Phenyl alanine
and tyrosine comes from
phosphoenolepyruvate.
• Pyruvate used to make
alanine, valine, leucine and
isoleucine.

10. • Aspartate is formed from
oxaloacetate and
aspartate is used to make
other amino acids like
aspargine, methionine,
threonine and lysine.
• Glutamate is synthesized
from @ ketoglutarate
.And from glutamate
more amino acids like
glutamaine, proline and
arginine can be
synthesised

11. Glutamate is synthesized from ammonia and -
ketoglutarate by the action of glutamate dehydrogenase.
A second ammonium ion is incorporated into glutamate
by the action of glutamine synthetase to form glutamine

12. • Proline is a cyclized derivative of
glutamate.
• In the first step of proline
synthesis, ATP reacts with the
side chain carboxyl group of
glutamate to form an acyl
phosphate, which is reduced by
NADPH or NADH to glutamate γ-
semialdehyde.
• This intermediate undergoes
rapid spontaneous cyclization
and is then reduced further to
yield proline.

13. • Arginine is synthesized
from glutamate via
ornithine and the urea
cycle in animals

14. • Serine, Glycine and Cysteine are derived
from 3-Phosphoglycerate .
• The major pathway for the formation of
serine is the same in all organisms
• In the first step, the hydroxyl group of 3-
phosphoglycerate is oxidized by
dehydrogenase (using NAD) to yield 3-
phosphohydroxypyruvate.
• Transamination from glutamate yields 3-
phosphoserine, which is hydrolyzed to free
serine by phosphoserine phosphatase.
• Serine (three carbons) is the precursor of
glycine (two carbons) through removal of a
carbon atom by serine hydroxy methyl
transferase.

15. • Plants and bacteria produce the reduced
sulfur required for the synthesis of cysteine
(and methionine) from environmental sulfates
• Mammals synthesize cysteine from two amino
acids: methionine furnishes the sulfur atom,
and serine furnishes the carbon skeleton.

16. Biosynthesis of Aspartate

17. Aspartate Synthesis From
Oxaloacetate
• Aspartate is synthesize by the transfer of an ammonia group from
glutamate to oxaloacetate. Aspartate can be formed in a
transamination reaction. The transamination reaction is
catalyzed by aspartate transaminase. This reaction uses the α-
keto acid oxaloacetate as the amino acceptor and glutamate as
the primary amino group donor

18. Synthesis of Asparagine from
Aspartate
• Asparagine is synthesized from aspartate via an amidotransferase
reaction catalyzed by asparagine synthetase.

19. • Alanine can easily be synthesized from the
alpha-keto acid pyruvate by a transamination
reaction

20. Alanine synthesis from P y r u v a t e
There are two main pathways to production of muscle
alanine: directly from protein degradation, and via the
transamination of pyruvate by alanine transaminase
(ALT).

21. Synthesis of valine and leucine
• The pathway of valine biosynthesis is a four-step
pathway.
• Aceto lactate synthase transfers the acyl group of
pyruvate to another molecule of pyruvate,
forming acetolactate. This is the 1ststep in the
biosynthesis of the amino acids valine and leucine
• In the 2nd step acetolactate is converted into 2,3-di
hydroxyisovalerate in the presence of
acetohydroxyacid reductoisomerase.
• In 3rd step Dihydroxyacid dehydratase enzyme
convert2,3-di hydroxyisovalerate into 2-keto-
isovalerate.
• In 4th step 2-keto-isovalerate conevted into Valine
and leucine with the help of transferase enzymes.

22. Aromatic amino acids
• Aromatic amino acids are amino acids
that include an aromatic ring.
– Phenylalanine
– Tryptophan
– Tyrosine
– Histidine

23. • Phenylalanine, tryptophan, and histidine are
essential amino acids for animals.
• Since they are not synthesized in the human
body, they must be derived from the diet.
• Tyrosine is semi-essential; it can be
synthesized, but only from phenylalanine.
• A lack of the enzyme phenylalanine
hydroxylase, used in tyrosine synthesis,
causes phenylketonuria and concurrently
renders tyrosine an essential amino acid.

24. • Synthesis of the aromatic amino acids begins with
the synthesis of chorismate - an important
intermediate for many biosynthetic pathways.
• Phosphoenol pyruvate and erythrose 4-phosphate
serve as beginning substrates for the pathway.
• A price of one NADPH + H+ and one ATP is used
for every chorismate formed.
• In the sixth step of the synthesis another
phosphoenol pyruvate molecule is added to the
growing molecule
Biosynthesis of Aromatic amino acids

26. Biosynthesis of Tryptophan
• Tryptophan synthesis is complex and involves 5 steps from chorismate.
• Glutamate donates an amine group in the first step of the pathway and pyruvate is lost
from chorismate.
• In the next threes steps a ribose sugar is added, this eventually contributes to the 5
membered ring of tryptophan.
• Energy is contributed to the process in the form of hydrolysis of pyrophosphate.
• This hydrolysis helps drive the addition of the ribose sugar in the second step of the
reaction.
• In the last step of the pathway serine serves as the donor of the carbon amino group of
tryptophan.

27. Biosynthesis of Phenylalanine and
Tyrosine
• Phenylalanine
– Chorismate is converted
to phenylpyruvate in two
steps
– No energy is required to
run these reactions

28. • Phenylalanine is synthesized
by a transamination reaction
with glutamate.
Tyrosine
The synthesis of tyrosine is
very similar to the synthesis
of phenylalanine, but the
reactions are carried out by
different enzymes under
different regulatory control.

29. Biosynthesis of Histidine
• The synthesis of histidine is
long and complex and its
pathway is intertwined with
nucleic acid biosynthesis
(specifically purine).
• The first five steps of the
pathway take ribose from
phosphoribosyl
pyrophosphate (PRPP) and
transform it into Imadiazole
glycerol phosphate.
• Once the imadiazole ring is
formed, glutamate donates
the α-amino group and the
newly formed amine is
oxidized to histidine in the last
step of the pathway.

30. Regulation of Amino Acid Biosynthesis
1 Feedback Inhibition
The end products of biosynthesis often inhibit
key enzymes to prevent overproduction of
amino acids.
2 Genetic Regulation
Gene expression is regulated to modulate the
production of enzymes involved in amino acid
biosynthesis.
3 Cellular Signaling
Cell signaling pathways play a role in sensing
amino acid levels and adjusting biosynthesis
accordingly.

31. Significance of Amino Acid Biosynthesis
in Cellular Metabolism
Energy Production
Amino acids contribute to energy
production through the citric acid
cycle.
Protein Synthesis
Amino acids serve as the
building blocks for proteins,
essential for various cellular
processes.