Download MBBS Biochemistry PPT 38 Biosynthesis Of Non Essential Amino Acids Lecture Notes

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