What does coenzyme mean?
A coenzyme is a small, non-protein organic molecule that works alongside enzymes to make biochemical reactions possible. Enzymes themselves are proteins, but many cannot function unless the right coenzyme is bound to them; the coenzyme typically acts as a temporary carrier, ferrying electrons, atoms, or chemical groups between molecules during a reaction. Well-known examples include NAD+, FAD, and coenzyme A, all of which participate in the metabolic pathways that extract energy from food. Most coenzymes are synthesized from vitamins, which explains why a deficiency of a single vitamin can disrupt entire chains of chemistry in the body. The term appears mainly in biochemistry, nutrition, and medicine, and it is related to but distinct from 'enzyme' and the broader term 'cofactor'. Understanding coenzymes helps clarify how vitamins support health and how cellular metabolism operates.
nounA non-protein organic molecule that binds to an enzyme and is essential for its activity, often functioning as a carrier of electrons, atoms, or functional groups in the chemical reactions the enzyme catalyzes. Many coenzymes are derived from vitamins.
- A small organic, non-protein molecule required for an enzyme's catalytic activity, typically serving as a transient carrier of electrons, atoms, or chemical groups between reactions; most are derived from vitamins.
"NAD+ is a coenzyme that shuttles electrons during cellular respiration."
"The mitochondria depend on coenzymes such as FAD to transport electrons along the respiratory chain."
"Because the body cannot synthesize it directly, niacin from the diet is converted into the coenzyme NAD+ needed by hundreds of enzymes."
Regular plural formed by adding -es; standard in both British and American scientific writing.
"B vitamins serve as precursors to several essential coenzymes involved in energy metabolism."
Your body can't run without coenzymes like NAD+ — and many of them are just rearranged vitamins you ate at breakfast.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coenzyme
The word coenzyme was formed in the early twentieth century from the prefix co- ('together, jointly') combined with 'enzyme', reflecting its role as a substance that works together with an enzyme. 'Enzyme' itself derives ultimately from Greek roots meaning 'in leaven' (en + zymē, 'leaven' or 'yeast'), coined when these catalysts were first studied in fermentation. English words sharing this Greek root include 'zymurgy', the branch of chemistry dealing with brewing and fermentation.
Related word forms
How coenzyme is actually used
Coenzyme is a technical term used chiefly in biochemistry, molecular biology, nutrition science, and medical writing; it rarely appears in casual conversation. It carries no figurative or informal senses. In scientific usage, specific coenzymes are usually referred to by abbreviations (NAD+, FAD, CoA) once introduced.
Easily confused with coenzyme
An enzyme is a protein that catalyzes a biochemical reaction, whereas a coenzyme is a small non-protein molecule that assists the enzyme in doing so.
Cofactor is the broader term for any non-protein helper substance, while a coenzyme is specifically an organic cofactor, often vitamin-derived.