Page 65 - Medicinal Plants_PharmD general

Cofactor:

1. Cofactor is any substance (other than the substrate) whose presence is
essential for the activity of an enzyme “helper molecules”. (Figure 12).

2. The cofactor can be:
a) Inorganic metal ions such as zn2+, Cu2+, Mn2+, K+ and Na+
b) Small organic molecules called coenzymes (NAD+, NADP+, ATP
and coenzyme A).

Figure 12. Cofactor

Coenzyme:

1. Coenzyme is an organic non-protein molecule that is a functional part
of an enzyme.

2. Coenzyme acts as transporters of chemical groups from one reactant to
another

3. The chemical groups carried can be hydride ion (H+,2e) carried by
NAD+ or NADP+ Or COCH3 carried by coenzyme A or transfer of
chemical energy carried by ATP.

Three coenzymes that will be particularly important in our study of
plant metabolism are listed in Table 1. You will note that the first two of
these NAD and NADP, serve as carriers of hydrogen (electrons) between
two different reactions in the cell. The third is CoA, which acts as a carrier
of an organic group containing two carbon atoms. It receives the group in
one enzymatic reaction and may act as a coenzyme in another enzyme
reaction where the two-carbon-atoms group is used.

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