MSH: Biological molecules that possess catalytic activity. They may occur naturally or be synthetically created. Enzymes are usually proteins, however CATALYTIC RNA and CATALYTIC DNA molecules have also been identified.,CSP: protein molecules that possess catalytic activity; they may occur naturally or be synthetically created; for catalytic RNA use RIBOZYME.,NCI: A protein that speeds up chemical reactions in the body.,NCI: Molecules that catalyze a chemical reaction. They are usually proteins, although catalytic RNA and DNA molecules have been identified.