- A protein that acts as a catalyst in biological systems.
- a protein that contains a catalytic site for a biochemical reaction
Source: Jenkins, John B. 1990. Human Genetics, 2nd Edition. New York: Harper & Row
- catalyst that is secreted by protoplasm to bring about or hasten a reaction, but that is not consumed in the process
Source: Noland, George B. 1983. General Biology, 11th Edition. St. Louis, MO. C. V. Mosby