Enzyme invoved in eukarotic translation

1. ENZYME INVOLVED
IN EUKARYOTIC
TRANSLATION
BY: Khushboo Arya

2. CONTENTS
• Introduction of translation
• Enzymes
i. Amino acyl tRNA– synthetase enzyme
ii. Peptidyl transferase
• Structure and function of amino acyl t- synthetase
enzyme
• Structure and function of peptidyl transferase enzyme
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3. TRANSLATION
• It is a process of synthesis of proteins directed by a mRNA template .
• The information in form of three nucleotide sequence of mRNA is
read as the three letter words known as (triplet ),codons.
• Each word stands for one amino acid .
• During translation amino acid linked together to form a polypeptide
chain of protein.
.
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4. TRANSLATION MACHINERY
•The machinery required for translating the language of mRNA
into the language of protein is composed of four components
• mRNA
• tRNA
• Enzymes
I. Amino acyl tRNA - synthetase enzyme
II. Peptidyl transferase
• Ribosome
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5. AMINOACYL tRNA SYNTHETASE
ENZYME
 It is an enzyme that attaches the appropriate amino acid on
its tRNA .
 It catalyze the esterification of specific amino acid .
 The accuracy of protein translation depends upon its fidelity with
which the correct amino acid are esterified to their cognate tRNA
molecule by amino acyl tRNA synthetase.
This enzyme catalyzes the union of amino acid and tRNA.
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7. ATTACHMENT OF AMINO ACIDS TO tRNA
Amino acids are attached to tRNA in two steps:
a) ADENYLATION : Amino acid react with the ATP to
become adenylated and carboxylic group of amino
acids is ionized to phosphate group of AMP by
releasing PPi from ATP.
b) CHARGING: Carboxylic group of adenylated amino
acids react with 3’OH of tRNA . A high energy bond and
a concomminent release of AMP.
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8. tRNA CHARGING MECHANISM
Step 1 : The amino acids and a molecule of ATP enter the
active site of enzyme .
 The ATP loses the pyrophosphate and resulting AMP
bond covalently to the amino acid. The pyrophosphate
hydrolyze into two phosphate groups.
Step 2 : the TRNA covalently bonded to amino acids to
displace the AMP and amino acyl tRNA release from the
enzyme.
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12. AMINO ACYL tRNA SYNTHETASE
•There is one synthetase enzyme for each amino acid .
•A single synthetase recognize multiple tRNAs for the same
amino acid
 Two classes of synthetase :
•Different in 3d structure.
•Differ in which side of the tRNA they recognize and how they bind ATP.
 CLASS 1: monomeric , acylates the 2’OH on terminal ribose Arg , Cys
, Leu , Met , etc.
 CLASS 2 : dimeric, acylates the 3’OH on terminal ribose Ala ,Asp ,
Gly,His etc.
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13. PEPTIDYL TRANSFERASE
ENZYME
 The peptidyl transferase enzyme is an amino acyl transferase
as well as the primary enzymatic function of the ribosome, which
form peptide bond between adjacent aminoacids using tRNAs
during the translation process of proteins.
 The substrate for the peptidyl transferase reaction are two
tRNA molecule, one bearing the growing peptide chain and
other bearing the amino acids that will be added to chain
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15. PEPTIDYL TRANSFERASE
REACTION
Once the correctly charged tRNA has been placed in the A site
has rotated in peptidyl transferase centre peptide bond formation
takes place.
This reaction is catalyzed by 23S rRNA component of large
subunit .
So ribosome also known as ribozyme .
Base pairing between the 23S rRNA and the CCA end of RNA in
the A site and P site help to position the alpha amino group of the
amino acyl tRNA to attack the carbonyl group of the growing
polypeptide chain attached to the peptidyl tRNA.
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18. THANK YOU
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Khushbu Arya