Biochemistry, Vol. 1 - A. Lehninger 1985

Biomolecules
Vitamins and Trace Elements: Their Role in Enzyme Function
Animal diets must contain numerous inorganic substances

For normal growth and biological function, humans and animals require a wide range of inorganic elements In addition to Vitamins. These elements can be divided into two classes: Macronutrients and micronutrients. Macronutrients, which include calcium, magnesium, sodium, potassium, phosphorus, sulfur, and chlorine, are needed by the body in relatively large quantities (on the order of several grams per day). They frequently fulfill more than one function. For example, calcium serves as a structural component of the inorganic bone substance hydroxyapatite, the composition of which can be roughly described by the formula [Са3 (РО4)2]3. At the same time, Са2+ ions act as crucial regulators in The Cell Cytosol, where their concentration is less than 10-6 M. Phosphorus, in the form of phosphate, is an essential component of the intracellular ATP-dependent energy transfer system.

Of more direct relevance to enzyme action are essential Trace Elements (Tables 10-2 and 10-3), the daily requirement for which does not exceed a few milligrams or micrograms—comparable, that is, to the requirement for vitamins. It is well established that the diet of animals must contain approximately 15 trace elements.

Most essential trace elements serve as Cofactors or prosthetic groups for Enzymes, fulfilling at least one of three possible Functions. First, the essential trace element itself may exhibit catalytic activity toward a specific chemical reaction, The rate of which is significantly enhanced in the presence of the enzyme protein. This is particularly characteristic of Iron and copper ions. Second, a metal ion can form a complex simultaneously with both the substrate and the Active Site of the enzyme, thereby bringing them into close proximity and converting them into an active form. Finally, the metal ion can act as a potent electron acceptor at a specific stage of the catalytic cycle. Enzymes whose activity requires Metal Ions are frequently referred to as metalloenzymes.

Class="center">Table 10-2. Trace elements and their biological functions

Element

Examples of biochemical functions

Iron

Prosthetic group of heme-containing enzymes (catalase, cytochrome oxidase)

Iodine

Essential for the synthesis of THYROID Hormones

Copper

Prosthetic group of cytochrome oxidase

Manganese

Cofactor for arginase and Other Enzymes

Zinc

Cofactor for dehydrogenase, DNA polymerase, Carbonic anhydrase

Cobalt

Component of vitamin B12

Molybdenum

Cofactor for xanthine oxidase

Selenium

Cofactor for Glutathione peroxidase and other enzymes

Vanadium

Cofactor for nitrate reductase

Nickel

Cofactor for urease

Table 10-3. Essential trace elements whose biochemical functions have not yet been precisely established

Element

Putative function

Chromium

Normal utilization of Blood glucose

Tin

Bone Formation

Fluorine

Bone formation

Silicon

Formation of Connective Tissue and bone

Arsenic

Unknown


Last update: 06/08/2026

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