The ribonucleotide reductase is important for converting ribose bases to the deoxy form. This conversion is coupled with the oxidation of which compound?

Thioredoxin

Explanation:

Ribonucleotides serve as precursors for synthesis of deoxyribonucleotides and the reaction is catalyzed by enzyme ribonucleotide reductase. The reduction of a ribonucleotide into deoxyribonucleotide requires a pair of hydrogen atoms.

These hydrogen atoms are supplied from NADPH via ubiquitous protein thioredoxin. The oxidized form of thioredoxin is reduced back in a reaction catalyzed by thioredoxin reductase.