2. BIOSYNTHESIS OF AMINO
ACIDS
All amino acids are synthesized from
intermediates of Glycolysis, TCA or PPP.
Different organisms vary greatly in their
ability to synthesize the 20 amino acids.
Amino acids are grouped by their
metabolic precursors.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14. Several enzyme cofactors play important
roles in amino acid metabolism
One carbon transfer is very important
– Biotin
– Tetrahydrofolate
– S-adenosylmethionine (SAM)
26. Cys is made from Ser and HomoCys
Sulfur comes from homoCys
The C skeleton comes from Ser
High homocysteine levels are associated with
vascular diseases
• Coronary heart disease
• Arteriosclerosis
The molecular basis of the disease ???
• It appears to damage cells lining blood vessels
and to increase the growth of vascular smooth
muscle cells
27.
28. Amino acids are precursors of
many biomolecules
Glutathione (GSH)
Nitric oxide (NO)
29.
30. GSH serves as a buffer and antioxidant
Protects cells from oxidative damage
Presents at high levels (5 mM)
It cycles between a reduced form (GSH) and an
oxidized form (GSSG)
GSSG is reduced to GSH by GSH reductase
The ratio of GSH to GSSG is greater than 500 in
most cells.
GSH plays a key role in detoxification by reacting
with hydrogen peroxide and organic peroxides.
Glutathione peroxidase is remarkable in having a
modified amino acid containing Se.
36. Nitric oxide is formed from Arg
NO is an important messenger
It is made by NO synthase
NADPH and Oxygen are required
37.
38. Amino acids are converted to
specialized products
Porphyrins and bile pigments
– Biosynthesis of porphyrins
• Formation of ALA
• Formation of porphobilinogen
Porphyrias
– Congenital erythropoietic porphyria
