Dictionary > Apoenzyme


noun, plural: apoenzymes
(biochemistry) The protein component in which together with a cofactor forms a complete enzyme
Enzymes can speed up biochemical processes. Some enzymes need cofactors (non-protein molecules) to carry out catalysis while others do not. Those that do not require cofactors are referred to as simple enzymes. Examples are pepsin, trypsin, and urease. Those that require a particular cofactor are referred to as conjugate enzymes.
Conjugate enzymes are comprised of two main components: (1) cofactor, which is the non-protein part and (2) apoenzyme, the protein part. The cofactor may be an organic compound (e.g. flavin) or an inorganic compound (e.g. metal ion). The organic cofactor may either be a coenzyme or a prosthetic group. A coenzyme is a cofactor that is loosely bound to the enzyme and therefore may be released readily from the active site of the enzyme. Examples of coenzymes are those made of water-soluble vitamins (i.e. B vitamins and vitamin C), and elements (e.g. Cu, Ca, Zn, Mg, K, Ni, Co, Fe, etc.).1 A prosthetic group is rather firmly attached to the enzyme.
The term holoenzyme is used to refer to the apoenzyme bound to a cofactor.
See also:


1 Jain, V.K. and Sharma, J.P. (2005). Comprehensive Objective Biology. New Delhi, India: Golden Bells. p.99

You will also like...

Plant meristem
Plant Meristems and Growth

In plants, growth occurs in meristems, which are the site of repeated cell division of unspecialized cells. These cells ..

temperature - abiotic factor
Abiotic and Biotic Factors

This tutorial deals with the abiotic factors of the freshwater environment that determine what sort of life would be sui..

Biological Cell Defense
Biological Cell Defense

Organisms employ different strategies to boost its defenses against antigens. Humans have an immune system to combat pat..

Plant biology
Plant Biology

Plantlife can be studied at a variety of levels, from the molecular, genetic and biochemical level through organelles, c..


Humans are diploid creatures. This means that for every chromosome in the body, there is another one to match it. Howeve..

"Cronopio dentiacutus", a prehistoric mammal (an illustration)
Mammalian Ancestors

Mammals are a diverse group of organisms, where most of them develop their offspring within the uterus of the mother. Ov..