Download MBBS (Bachelor of Medicine, Bachelor of Surgery) 1st year (First Year) Biochemistry ppt lectures Topic 38 Biosynthesis Of Non Essential Amino Acids Notes. - biochemistry notes pdf, biochemistry mbbs 1st year notes pdf, biochemistry mbbs notes pdf, biochemistry lecture notes, paramedical biochemistry notes, medical biochemistry pdf, biochemistry lecture notes 2022 ppt, biochemistry pdf.
Biosynthesis of non-essential amino
acids
Department of Biochemistry
Specific Learning Objectives
1. Biosynthesis of non-essential amino acids (body can synthesize them
from other proteins so not essential to eat them)
Essential and non-essential amino acids
? Essential
aa:
Cannot
be
synthesize in body so "essential"
to eat them from dietary food.
? Non-essential:
Body
can
synthesize them from other
proteins so not essential to eat
them
Table 27.1. Harper's Illustrated Biochemistry 30th Edition
Overview of amino acid biosynthesis
Fig22.11: Lehninger Principles of Biochemistry by David L Nelson, 6th Ed.
Glutamate
? Glutamate, is formed by the amidation of -
ketoglutarate, catalyzed by mitochondrial
glutamate dehydrogenase
? It require NADPH as a reducing agent
? The reaction strongly favors glutamate
synthesis, which lowers the concentration of
cytotoxic ammonium ion.
Glutamine
? Amidation of glutamate to glutamine catalyzed by
glutamine synthetase, involves intermediate formation of
-glutamyl phosphate
? In Binding of glutamate and ATP, glutamate attacks -
phosphorus of ATP, forming -glutamyl phosphate and
ADP
? NH4+ binds, and uncharged NH attacks -glutamyl
3
phosphate
? Release of Pi and of a proton from -amino group of
tetrahedral intermediate then al ows release of product,
glutamine
Alanine & Aspartate
? Transamination of pyruvate forms
alanine
? Similarly,
transamination
of
oxaloacetate forms aspartate
Asparagine
? Conversion of aspartate to asparagine,
catalyzed by asparagine synthetase
? Reaction involves intermediate formation of
aspartyl phosphate
? Coupled hydrolysis of PPi to Pi by
pyrophosphatase, ensures that reaction is
strongly favored
Serine
? Oxidation of -hydroxyl group of glycolytic
intermediate 3-phosphoglycerate, catalysed
by 3-phosphoglycerate dehydrogenase,
converts it to 3-phosphohydroxypyruvate
? Transamination
and
subsequent
dephosphorylation then form serine
Glycine
? Glycine aminotransferases can catalyze
synthesis of glycine from glyoxylate and
glutamate or alanine.
? Unlike most aminotransferase reactions, these
strongly favor glycine synthesis
? Important mammalian routes for glycine
formation are from choline
Cont--
? Glycine formation are from
serine
Proline
? Initial reaction of proline biosynthesis converts
-carboxyl group of glutamate to mixed acid
anhydride of glutamate -phosphate
? Subsequent reduction forms glutamate -
semialdehyde, which following spontaneous
cyclization is reduced to proline
Cysteine
? While not nutritionally essential, cysteine is
formed from methionine, which is nutritionally
essential
? Following conversion of methionine to
homocysteine, homocysteine and serine form
cystathionine, whose hydrolysis forms cysteine
and homoserine
Tyrosine
? Phenylalanine hydroxylase converts phenylalanine to
tyrosine
? Phenylalanine hydroxylase reaction is irreversible,
dietary tyrosine cannot replace phenylalanine
? Catalysis by this mixed-function oxidase incorporates
one atom of O2 into para position of phenylalanine
and reduces other atom to water
? Reducing power, provided as tetrahydrobiopterin
derives ultimately from NADPH
Valine, Leucine, & Isoleucine
While leucine, valine, and isoleucine are all nutritionally essential
amino acids, tissue aminotransferases reversibly interconvert all
three amino acids and their corresponding -keto acids
These -keto acids thus can replace their amino acids in diet
Hydroxyproline & Hydroxylysine
? Peptidyl hydroxyproline and hydroxylysine
arise from proline and lysine
? Hydroxylation of peptidyl prolyl and peptidyl
lysyl residues, catalyzed by prolyl hydroxylase
and lysyl hydroxylase of skin, skeletal muscle,
and granulating wounds requires, in addition to
the substrate, molecular O2, ascorbate, Fe2+,
and -ketoglutarate
? For every mole of proline or lysine
hydroxylated, one mole of -ketoglutarate is
decarboxylated to succinate
? A deficiency of the vitamin C required for these
two hydroxylases results in scurvy
Two Clinical-cases discussed
Group Discussion and Rivision
Subtopics of previous and today's class discussed in groups.
Reference Books
19
1) Lehninger Principles of Biochemistry, 6th Ed.
2) Harper's Il ustrated Biochemistry-30th edition
3) Biochemistry, Lippincott's Il ustrated Reviews, 6th Ed
4) Gregory S. Ducker and Joshua D Rabinowitz. Cell Metab. 2017 Jan
10;25(1):27-42
Thank you
This post was last modified on 05 April 2022