Biochemistry

The carboxypeptidase-containing Zn 2+ enzyme catalyzes the breakdown of a protein molecule or other peptide. In this case, the peptide bond is cleaved, which is located next to the free carboxyl group — COOH. Another well-studied Zn-containing enzyme is a carbonic anhydrase. The physiological role of this enzyme is the rapid reversible cleavage of carbonic acid. Due to this enzyme, in the animal and human body, there is a rapid hydration of CO 2 , which is formed during respiration in tissues, and its subsequent dehydration in the lungs. Human carbonic anhydrase is, apparently, the most "fast ­ working" enzyme: in 1 second, it provides hydration of 600 thousand molecules of CO 2 . Zinc plays an important role in other key metabolic processes in the body. It is known that this metal, along with others (Cu, Fe, Mn, Co, Ni), is directly involved in maintaining the secondary and tertiary structure of DNA and RNA. Zn 2+ is also required for the functioning of DNA-polymerase and transcriptase enzymes. A lack of zinc in the animal ’ s body leads to growth retardation, impaired formation of the coat, and especially the functions of the gonads. At the same time, zinc compounds such as ZnO, ZnCl 2 , ZnSO 4 for humans and animals in large quantities are toxic. Zinc poisoning is accompanied by headache, anorexia, anemia, emaciation, heart disorders, and kidney failure. The magnesium content in the earth's crust is about 2%. Magnesium plays an extremely important role in maintaining life on Earth. Its Mg 2+ cations are part of chlorophyll - photopigment, which is the link between the energy of the Sun and the Earth's biosphere. In addition, this metal activates key nucleic acid metabolism enzymes - DNA polymerase, RNA polymerase and others. The role of Mg 2 ’ in protein synthesis is also irreplaceable. Magnesium is located in the ribosomes in a state bound to proteins and nucleic acids and regulates the functioning of these major organelles of the cell. It turned out that ribosomes are stable only at a Mg 2+ concentration close to 0.001 M. With a decrease in the concentration of this cation to 0.0001 M, the ribosomes decompose into subparticles and protein synthesis is interrupted. On the contrary, when the Mg 2+ content is increased to 0.01 M, ribosomes give dimers and stick together to larger aggregates. An increased concentration of magnesium in biological media, as it turned out, increases the number of errors when reading the protein synthesis code (genetic code). Magnesium ions, in addition, are included in the complex of contractile muscle protein of myosin and ATP. By activating the breakdown of ATP macroergic bonds, they thereby contribute to the release of energy for muscle contractions. 15