Lecture_23_4-22-10-PDF_41871

Lecture_23_4-22-10-PDF_41871 - Lec-23, Nucleotide...

Info iconThis preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
3. Formation of Deoxyribonucleotides A. Production of Deoxyribose residues B. Origin of Thymine Lec-23, Nucleotide metabolism
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chapter 3
Background image of page 2
Synthesis of Deoxynucleotides Ribonucleotide reductase Deoxyribonucleotides (dNDP) are synthesized by the reduction of the hydroxyl group at C2’ of the corresponding ribonucleotide.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The linkage of RNA to a ‘DNA world’ raises the possibility that ribonucleotide reductases might be important in this process. RNA to a ‘DNA world’ Ribonucleotide reductase
Background image of page 4
An enzyme that controls the cellular concentration of deoxyribonucleotides (DNA) Ribonucleotide reductase Ribonucleotide reductase
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Knowledge of the catalytic mechanism of RNRs is the result of extensive studies of the prototypical members of the three well-characterized classes . Ribonucleotide reductase 1. Class I is represented by E. coli aerobic RNR 2. Class II by the Lactobacillus leichmannii RNR 3. Class III by E. coli anaerobic RNR
Background image of page 6
Ribonucleotide reductase All RNRs catalyze the cleavage of a 2′ carbon– hydroxyl bond with the formation of a 2′ carbon– hydrogen bond.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Ribonucleotide reductase Class I E. coli aerobic RNR Fe(III)=Fe 3+ , ferric Fe(II)=Fe 2+ , ferrous R1 R2
Background image of page 8
Ribonucleotide reductase Class I E. coli aerobic RNR 1. R1 contains the substrate binding site with several redox active sulfhydral residues (SH) and two independent effector-binding sites which controls the activity of the enzyme. 2. R2 contains a unique Fe(III) cluster liganded by O -2 and interacts with a tyrosine (122) that forms a stable free radical .
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Cofactor A small organic molecule (coenzyme) or metal ion that is required for the catalytic activity of an enzyme From Voet G-6, Glossary Coenzyme A small organic molecule that is required for the catalytic activity of an enzyme. A coenzyme may be either a cosubstrate or a prosthetic group Cosubstrate A coenzyme that is only transiently associated with an enzyme so that it functions as a substrate Prosthetic group A cofactor that is permanently (often covalently) associated with an enzyme Supplemental
Background image of page 10
Reaction catalyzed by RNR: three classes I, II, and III E SH SH E S S Class I and II --- Anaerobic conditions HCO 2 - CO 2 Class III
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The mechanism of ribonucleotide reductase (Class I) 5 steps Proposed by JoAnne Stubbe (MIT Chemistry) http://web.mit.edu/biochemistry/rnr.html
Background image of page 12
Image of page 13
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 54

Lecture_23_4-22-10-PDF_41871 - Lec-23, Nucleotide...

This preview shows document pages 1 - 13. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online