Zinc, biological role

M. Chvapil, New aspects in the biological role of zinc A stabilizer of macromolecules membranes. Life Sci. /5 1041 (1973). 

The Biological Role of Zinc Coordination Chemistry Zinc Metalloenzymes 1001... 

Biological Roles of Zinc and Copper. Zinc and copper are essential cofactors at the active site of a number of enzymes. Zinc is a component of more than 200 proteins and enzymes (Table II). Copper, sim-lleT to iron, participates both in redox reactions and as a proton doner (Table III). The normal human adult body contains approximately 50-100 mg of copper and 2.0 g of zinc. The vast majority of tissue copper is found in the liver, kidney, heart and brain. In the blood, copper exists within the red blood cell as superoxide dlsmutase and in the serum as ceruloplasmin. Copper is a component of aerobic metabolism, bone synthesis, and erythrocyte development. Zinc is found primarily in the liver, kidney, bone and prostate. Zinc is essential for normal growth of tissues, wound repair, skin structure, reproduction, taste perception, and the prevention of dwarfism. 

Table 1 Biologic roles of the zinc-dependent proteinases categorized into four subgroups based on the conserved structural motif of their active site (5)...

One of the most important discoveries concerning the biological role of zinc occurred in 1940 when Keilin and Mann showed that zinc is an essential compound of erythrocyte carbonic anhydrase, an enzyme cata-lytically involved in the transport of CO2 in blood (6). Following the 70-year interval between the initial recognition of a metabolic zinc deficiency and the characterization of the first zinc metalloenzyme, there was a period of about 15 years before the second zinc enzyme was identified. In 1955, Vallee and Neurath reported that carboxypeptidase A from bovine pancreas contained 1 g-atom Zn per mol of protein and was essential to the function of the enzyme (7). The presence of zinc in carbonic anhydrase and carboxypeptidase A indicated that a primary role of zinc would be to function in zinc metalloenzymes (62). However, it seemed unhkely that disrupting the activity of carboxypeptidase A or carbonic anhydrase would have profound eflFects on growth. 

A cofactor can be either an inorganic ion, such as Zn ", or a small organic molecule, called a coenzyme. The requirement of many enzymes for inorganic cofactors is the main reason for our dietary need of trace minerals. Iron, zinc, copper, manganese, and numerous other metal ions are all essential minerals that act as enzyme cofactors, though the exact biological role is not known in all cases. 

We will illustrate some of the processes involved in a eutrophic lake. Points of interest are the factors that determine the speciation of copper and zinc, the role of biologically produced ligands, how copper and zinc are bound in the settling particles, and whether the settling particles reflect the composition of algae with respect to trace elements. 

Zinc plays an important role as an essential trace element in all living systems from bacteria to humans. The detection of the zinc metalloenzymes and their biological role gradually proved to be a substantial contribution to a better understanding of zinc metabolism and its interactions with other essential and nonessential trace metals. 

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