Question

Six enzyme classes have been recognized and approved by International Union of Biochemistry since 1961. In 2018, which one of the following group of enzymes has been added as the seventh class, with Enzyme Commission number 7 (EC 7), by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB)?

• A. Racemases
• B. Translocases
• C. GTPases
• D. Ubiquitinases

Hint:

To remember the seven classes in order, use the mnemonic: "Over The Hill, Lyases Isomerize Ligands and Translocates" (Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, Ligases, Translocases).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Enzymes are systematically classified by the Enzyme Commission (EC) of the International Union of Biochemistry and Molecular Biology (IUBMB) based on the specific chemical reactions they catalyze.
For over five decades, the system recognized six primary classes of enzymes.

Step 2: Detailed Explanation:
The traditional six classes of enzymes established in 1961 are:
1. EC 1: Oxidoreductases
2. EC 2: Transferases
3. EC 3: Hydrolases
4. EC 4: Lyases
5. EC 5: Isomerases
6. EC 6: Ligases
In August 2018, the NC-IUBMB officially introduced a new, seventh class of enzymes:
EC 7: Translocases.
Translocases are enzymes that catalyze the transport of ions or molecules across membranes or their separation within membranes.
Prior to 2018, many of these enzymes (like ATPases or transport proteins) were classified under hydrolases (EC 3) because their transport action is often coupled with ATP hydrolysis.
However, because the primary physiological reaction is the translocation of a solute across a biological membrane, they were assigned their own dedicated class (EC 7) to improve classification accuracy.
Racemases belong to Isomerases (EC 5), and GTPases belong to Hydrolases (EC 3).

Step 3: Final Answer:
Translocases were added as the seventh class (EC 7) in 2018, corresponding to option (B).