Cas12k is the large effector protein of type V-K CRISPR systems, which belong to the class 2 systems. Cas12k has also been known as C2c5, and type V-K as type V-U5. Type V-K CRISPR systems have also been known as with the large Cas12k protein, has also been known as type V-U5, and Cas12k as C2c5.