Download MBBS (Bachelor of Medicine, Bachelor of Surgery) 1st year (First Year) Biochemistry ppt lectures Topic 23 Biosynthesis 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.
Department of Biochemistry
Learning Objectives
1. Biosynthesis of non-essential amino acids:
? Alanine
? Asparagine & Aspartate
? Cysteine
? Glutamate
? Glutamine
? Glycine
? Proline
? Serine
? Tyrosine
? Hydroxyproline and Hydroxylysine
Biosynthesis of non-essential amino
acids
Table 27.1. Harper's Illustrated Biochemistry 30th Edition
Glutamate
? Glutamate, is formed by amidation of
-ketoglutarate,
catalyzed
by
mitochondrial
glutamate
dehydrogenase
? It require NADPH as a reducing agent
? This
reaction
strongly
favors
Fig 27.1. Harper's Illustrated Biochemistry 30th Edition
glutamate synthesis, which lowers
the
concentration
of
cytotoxic
ammonium ion.
Cont--
? NH4+ binds, and uncharged NH3 attacks -glutamyl phosphate
? Release of Pi and of a proton from the -amino group of the
tetrahedral intermediate then allows release of the product,
glutamine
Glutamine
? Amidation of glutamate to
glutamine catalyzed by glutamine
synthetase
? Glutamine, is amino group donor
in formation of many biosynthetic
products, as well as being a
Fig 27.2. Harper's Illustrated Biochemistry 30th Edition
storage form of ammonia
Cont--
? Mammalian Glutamine synthetases are activated by -
ketoglutarate, the product of glutamate's oxidative
deamination
? This prevents the accumulation of the ammonia produced by
that reaction
Alanine
? Transamination of pyruvate forms
alanine by aminotransferase
Fig.26.54. Biochemistry. 4th edition by Donald Voet and Judith G. Voet
Aspartate
? Transamination of oxaloacetate
forms
aspartate
by
aminotransferase
Fig.26.54. Biochemistry. 4th edition by Donald Voet and Judith G. Voet
Asparagine
? Conversion of aspartate to
asparagine,
by
amidation
reaction and catalyzed by
asparagine synthetase
? ATP is needed to activate the
receptor a carboxyl group
Fig 27.5. Harper's Illustrated Biochemistry 30th Edition
? Asparagine
is
readily
synthesized in most cells, but
some leukemic cells lost this
ability
Cont--
? Therapeutic approach for patients with asparagine synthetase
deficient tumors is treatment with exogenous asparaginase to
hydrolyze the bloodborne asparagine on which these cells rely
? Normal cells synthesize and degrade asparagine.
Serine
The pathway enzymes are:
? 3-phosphoglycerate dehydrogenase
? PLP-dependent aminotransferase
? Phosphoserine phosphatase.
Fig.26.58. Biochemistry. 4th edition by Donald Voet and Judith G. Voet
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
Fig 27.8. Harper's Illustrated Biochemistry 30th Edition
Cont--
Serine participates in glycine
synthesis in two ways:
1. Direct conversion of serine to
glycine by serine hydroxymethyl
transferase in a reaction that also
yields N5,N10-methylene-THF
Fig 27.9. Harper's Illustrated Biochemistry 30th Edition
2. Condensation of the N5,N10-
methylene-THF with CO2 and by the
glycine cleavage system
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
Fig 27.10. Harper's Illustrated Biochemistry 30th Edition
Cysteine
? While not nutritionally essential, cysteine
is formed from methionine
Cystathione -synthetase
? Require for formation of glutathione,
which is imp for transport of aa
? Homocystinuria occur due to deficiency
of cystathionine -synthase
Fig 27.11. Harper's Illustrated Biochemistry 30th Edition
Tyrosine
? Phenylalanine hydroxylase converts
phenylalanine to tyrosine
? Its irreversible reaction, dietary
tyrosine cannot replace phenylalanine
Fig 27.12. Harper's Illustrated Biochemistry 30th Edition
Cont--
? Catalysis by this mixed-function oxidase incorporates one atom
of O into para position of phenylalanine and reduces other
2
atom to water
? Reducing power, provided as tetrahydrobiopterin derives from
NADPH
Branched chain aa (Valine, Leucine, & Isoleucine)
? While leucine, valine, and isoleucine are all nutritionally
essential aa , tissue aminotransferases reversibly interconvert
all three aa and their corresponding -keto acids.
? These -keto acids can replace their aa 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
Fig 27.13. Harper's Illustrated Biochemistry 30th Edition
addition to the substrate, molecular
O2, ascorbate, Fe2+, and -
ketoglutarate
Cont--
? 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
Amino acid degradation and related
disorders
Summary of Amino acid Catabolism
Fig18.15: Lehninger Principles of Biochemistry by David L Nelson
Genetic disorders related to Amino-acid catabolism
Table 18.2: Lehninger Principles of Biochemistry by David L Nelson
Interaction with students
? Distributed subtopics of class to students for participate in group
discussion in next class.
Reference Books
1) Lehninger Principles of Biochemistry
2) Harper's Illustrated Biochemistry-30th Ed
3) Biochemistry, Lippincott's Illustrated Reviews, 6th Ed
4) Text Book of Medical Biochemistry by Chatterjee & Rana Shinde,
8th Ed
5) Biochemistry, Donald Voet and Judith G. Voet, 4th Ed.
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Thank you
This post was last modified on 05 April 2022