Ribonucleotide Reductase

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Introduction

Ribonucleotide reductase, RNR, is one of the major enzymes that aids in the synthesis of deoxyribonucleotides. These precursors of DNA are vital for DNA synthesis, so RNRs are required in all living cells to replicate and repair DNA. The reaction catalyzed through RNR is the only biochemical pathway that can synthesize new deoxyribonucleotide triphosphates (dNTPs). This enzyme has led to and contributed to the evolution of genetic material that exists today. RNR consists of three different classes: I, II, and III. The classes differ in which they require different metal cofactors in order to initiate the reaction. This then leads to different environmental factors affecting the enzyme and its different classes.

Function

The conversion from ribonucleotides to deoxyribonucleotides is a radically-based reaction. Organic free radicals are stored by RNR until they are needed for catalysis.

Disease

Relevance

Structural highlights

The structure of ribonucleotide reductase is composed of two components. One portion is the radical generator which produces and stores the radical. This portion is used to oxidize the substrate to its radical form which is the first step of the overall reaction. The second portion of the structure consists of a reductase. The reductase is the same for all three classes, but the radical generator differs.