Zinc is a cofactor for up to 300 enzymes in the body1. Enzymes that use zinc as a cofactor are known as metalloenzymes. Zinc is a cofactor for the antioxidant enzyme superoxide dismutase that converts superoxide to hydrogen peroxide, as shown below.
Figure 12.811 Superoxide dismutase uses zinc as a cofactor
Alcohol dehydrogenase uses 4 zincs per enzyme. Its role in ethanol metabolism is shown below2.
Figure 12.812 Ethanol metabolism3,4
Delta-aminolevulinic acid dehydratase (ALA dehydrogenase), which is involved in heme synthesis, uses 8 zincs/enzyme to form porphobilinogen, as shown below2.
Figure 12.813 ALA dehydrogenase requires zinc in the heme synthesis pathway5
The enzyme that cleaves the extra glutamates from folate so that it can be taken up into the enterocyte is a metalloenzyme2. The cleavage of folate is shown in the figure below.
Figure 12.814 The absorption of folate and folic acid
Other notable metalloenzymes include DNA and RNA polymerase2.
Zinc is also important for the formation of zinc fingers in proteins. Zinc fingers help proteins bind to DNA2.
Figure 12.815 Structure of a zinc finger, zinc is the green atom bound in the center6
Zinc is also important for growth, immune function, and reproduction2.
A recent Cochrane review concluded that when taken within 24 hours of the onset of symptoms, that zinc lozenges or syrup results in a significant decrease in the duration and severity of common cold symptoms7. Thus, commonly used zinc lozenges may be an effective way to combat the common cold. However, large amounts of zinc consumption can be problematic for copper and ultimately iron levels in the body, as described in the copper section.
References & Links
- Byrd-Bredbenner C, Moe G, Beshgetoor D, Berning J. (2009) Wardlaw's perspectives in nutrition. New York, NY: McGraw-Hill.
- Gropper SS, Smith JL, Groff JL. (2008) Advanced nutrition and human metabolism. Belmont, CA: Wadsworth Publishing.
- Singh M, Das RR. (2011) Zinc for the common cold (Review). The Cochrane Collaboration.