Definition:

Catalytic core domain (CCD)is aspecific region of an enzyme molecule that can directly bind to and catalyze a chemical reaction of a substrate. For enzymes that do not require cofactors, it consists of several or even a dozen amino acid residues that are far apart in primary structure but close to each other in tertiary structure; For enzymes that require cofactors, the cofactor or some part of its structure is often a component of the active site.