Difference Between Reductase and Oxidoreductase

The key difference between reductase and oxidoreductase is that reductase is an enzyme that catalyzes a reduction reaction, while oxidoreductase is an enzyme that catalyzes both oxidation and reduction reactions.

Redox reactions include both reduction and oxidation. During redox reactions, the oxidation states of the molecules or atoms are changed. Enzymes catalyze redox reactions. Oxidoreductase and reductase are two types of enzymes involved in redox reactions. Reductases catalyze reduction reactions (gaining of electrons) while oxidoreductases catalyze both oxidation (release of electrons) and reduction reactions (gaining of electrons).

CONTENTS

1. Overview and Key Difference
2. What is Reductase 
3. What is Oxidoreductase
4. Side by Side Comparison – Reductase vs Oxidoreductase in Tabular Form
5. Summary

What is Reductase?

Reductase is an enzyme that catalyzes a reduction reaction by lowering the activation energy needed for the reaction to occur. Reductases are a class of oxidoreductase. Reduction is the gain of electrons, and it is usually coupled with oxidation. As a result of reduction, the oxidation state of the ion decreases.

Dihydrofolate reductase, 5α-reductase, 5β-reductase, HMG-CoA reductase, methemoglobin reductase, ribonucleotide reductase, aldose reductase and thioredoxin reductase are several reductases. 5α-reductase catalyzes the irreversible reduction of testosterone to dihydrotestosterone.

What is Oxidoreductase?

Oxidoreductase is an enzyme that catalyzes the oxidation of one molecule and reduction of another molecule simultaneously.  In other words, oxidoreductases are able to catalyze both oxidation and reduction reactions (oxidoreduction reactions). They act as an oxidase for one reaction and reductase for another reaction. Therefore, they catalyze the transfer of electrons from one molecule (oxidant) to the reductant. They need the presence of oxygen or NAD+/NADP+ in order to act as electron acceptors. Oxidoreductases can be oxidases or dehydrogenases. Oxidases catalyze the reactions when molecular oxygen acts as an acceptor of hydrogen or electrons.  Dehydrogenases oxidize a substrate by transferring hydrogen to an acceptor that is either NAD⁺/NADP⁺ or a flavin enzyme.  Peroxidases, hydroxylases, oxygenases, and reductases are other types of oxidoreductases.

Oxidoreductases are involved in aerobic and anaerobic respiration reactions. They catalyze reactions of glycolysis, TCA cycle, oxidative phosphorylation, and in amino acid metabolism. Glyceraldehydes-3-phosphate dehydrogenase is an oxidoreductase that participates in glycolysis in the reduction of NAD+ to NADH. It can be illustrated as follows.

Pi + glyceraldehyde-3-phosphate + NAD⁺ → NADH + H⁺ + 1,3-bisphosphoglycerate

What are the Similarities Between Reductase and Oxidoreductase?

• Reductase and oxidoreductase are two types of enzymes which are proteins.
• Reductases are a subclass of oxidoreductase.
• Both enzymes catalyze the reactions which change the oxidation states of ions and molecules.
• They participate in both aerobic and anaerobic respiration reactions.

What is the Difference Between Reductase and Oxidoreductase?

Reductase and oxidoreductase are two types of enzymes. Reductase catalyzes the reduction reactions while oxidoreductase catalyzes both oxidation and reduction reactions. So, this is the key difference between reductase and oxidoreductase. Dihydrofolate reductase, 5α-reductase, 5β-reductase, HMG-CoA reductase, methemoglobin reductase, ribonucleotide reductase, aldose reductase and thioredoxin reductase are several reductases. Meanwhile, oxidases, dehydrogenases, peroxidases, hydroxylases, oxygenases and reductases are oxidoreductases.

Below infographic tabulates the differences between reductase and oxidoreductase.

Summary – Reductase vs Oxidoreductase

Redox reactions involve the transfer of electrons between chemical species. One molecule releases electrons (oxidation) while the other molecule gains electrons (reduction). Reductases are enzymes that catalyze reduction reactions. Oxidoreductases are enzymes that catalyze both the oxidation and reduction reactions.  Both reductases and oxidoreductases lower the activation energy of the reactions. Moreover, they change the oxidation states of the molecules participating in the reactions. Thus, this summarizes the difference between reductase and oxidoreductase.

Reference:

1. “What Are Oxidoreductases?”. Chem.Uwec.Edu, 2020, Available here.
2. “Reductase – An Overview | Sciencedirect Topics”. Sciencedirect.Com, 2020, Available here.

Image Courtesy:

1. “Ribonucleotide reductase R2 e coli” By Sponk (talk) – PDB-File: doi:10.2210/pdb1av8/pdb, rendered with PyMOL (0.99rc2) (Public Domain) via Commons Wikimedia
2. “D-Glyceraldehyde-3-phosphate-3D-balls”  By Jynto and Ben Mills – Derived from File:D-Glyceraldehyde-3D-balls.png and File:3-phosphoric-acid-3D-balls.png (Public Domain) via Commons Wikimedia