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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 6/2/2020 2 Khushbu Arya
- 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. . 6/2/2020 3
- 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 6/2/2020 4
- 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. 6/2/2020 5
- 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 3OH of tRNA . A high energy bond and a concomminent release of AMP. 6/2/2020 7
- 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. 6/2/2020 8
- 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 2OH on terminal ribose Arg , Cys , Leu , Met , etc. CLASS 2 : dimeric, acylates the 3OH on terminal ribose Ala ,Asp , Gly,His etc. 6/2/2020 12
- 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 6/2/2020 13
- 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. 6/2/2020 15
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