Metabolism of zinc

Bakka, A. and M. Webb. 1981. Metabolism of zinc and copper in the neonate changes in the concentrations and contents of thionein-bound Zn and Cu with age in the livers of the newborn of various mammalian species. Biochem. Pharmacol. 30 721-725. 

Gold sodium thiomalate provides a stimulus for liver, kidney and possibly other cells to change the body distribution of zinc and copper. Proteins such as metalloproteins, superoxide dismutase and metallothioneins19 help the cell carry out this task. These essential metals are important in the physiological processes relevant to rheumatoid arthritis, and thus it also appears possible that the gold complexes may mediate their antiarthritic activity through an effect on the metabolism of zinc and copper. 

The metabolism of zinc is influenced by hormones, stress situations, lipopolysaccharides, toxins, oxygen radicals, lipid peroxidations, etc. This may lead to fluctuations in the zinc concentration, mainly due to the induction of metallothioneine (MT), which is a transport and intracellular depot protein. One third of this protein consists of cysteine, which binds zinc, copper, cadmium, cobalt and mercury. This protects the body from toxic heavy metal... 

Numerous aspects relating to the metabolism of zinc in plants have not yet been sufficiently investigated. Thus, the specific mechanisms of zinc uptake (also via the leaves) and transport have still to be identified at the molecular level. Physiological reasons for the large discrepancies in zinc requirements of various plants must be found, and the processes of distribution of the metal in plants, especially the migration from the growth tissues to the seeds must be clarified. 

Laurant P, Drozbartholet C, Berthelot A. 1991. Effect of a long-term high magnesium intake on metabolism of zinc in Sprague Dawley male rats. Trace elements in Medicine 8(2) 70-73. 

Thomas DJ, Winchurch RA, Adler WH. 1989. Influence of age upon the metabolism of zinc in livers of C57BL/6J mice. Mech Ageing Dev 47 241-251. 

Snedeker, S.M. and Greger, J.L. (1983). Metabolism of zinc, copper, and iron as affected by dietary protein, cysteine and histidine. J. Nutr.. 113. 644-652. 

Asokan P, Tandon SK (1981) Effect of cadmium on hepatic metallothionein level in early development of the rat. Environ. Res 24 201-206 Bakka A, Webb M (1981) Metabolism of zinc and copper in the neonate changes in concentrations and contents of thionein-bound Zn and Cu with age in the livers of the newborn of various mammalian species. Biochem. Pharmacol 30 721-725 Bell JU (1980) Induction of hepatic metallothionein in the immature rat following administration of cadmium. Toxicol. Appl Pharmacol 54 148-155 Barltrop D, Khoo HE (1979) The influence of dietary minerals and fat on the absorption of lead. The Sci. Total Environ 6 265-273 Bushnell PJ, DeLuca HF (1981) Lactose facilitates the intestinal absorption of lead in weanling rats. Science 211 61-63... 

Mason R, Bakka A, Samarawickrama GP, Webb M (1981a) Metabolism of zinc and copper in the neonate accumulation and function of (Zu, Cu)-metallothionein in the liver of the newborn rat. Br. J. Nutr. 45 375-389 Mason R, Brady FO, Webb M (1981b) Metabolism of zinc and copper in the neonate ac-ciamulation of Cu in the gastrointestinal tract of the newborn rat. Br. J. Nutr. 45 391-399... 

Andrews GK, Gallant KR, Cherian MG (1987) Regulation of the ontogeny of rat liver metallothionein mRNA by zinc. Eur J Biochem 166 527-531 Andrews GK, McMaster MT, De SK, Paria BC, Dey SK (1993) In Suzuki KT, Imura N, Kimura M (eds) Cell-specific expression and regulation of the mouse metallothionein I and II genes in the reproductive tract and preimplantation embryo. Metallothionein III. Birkhauser, Basel, pp 363-380 Bakka A, Webb M (1981) Metabolism of zinc and copper in the neonate changes in the concentration and contents of the thionein bound Zn and Cu with age in the livers of the newborn of various species. Biochem Pharmacol 30 721-725 Bremner I (1993) Involvement of metallothionein in the regulation of mineral metabolism. In Suzuki KT, Imura N, Kimura M (eds) Metallothionein III. Birkhauser, Basel, pp 111-124... 

It is also known that the toxic effects of heavy metals may be reduced in many organisms by binding to specific ligands. Metallothionein plays a crucial role among these specific ligands. In relation to trace elements, MT might serve as an indicator of an environmental pollution and exposure to this pollution. Increased level of MT-I and -II in tissue(s) indicates an exposure to trace elements, respectively heavy metals. MT-III is non-inducible and probably plays an important role in the metabolism of zinc and elements that are involved in neurotoxicity [128]. 

Metabolic Functions. Zinc is essential for the function of many enzymes, either in the active site, ie, as a nondialyzable component, of numerous metahoenzymes or as a dialyzable activator in various other enzyme systems (91,92). WeU-characterized zinc metahoenzymes are the carboxypeptidases A and B, thermolysin, neutral protease, leucine amino peptidase, carbonic anhydrase, alkaline phosphatase, aldolase (yeast), alcohol... 

In addition to their endocrine disrupting properties, it must be appreciated that many of the chemicals in question possess more general toxic properties, which may be potentiated by metabolism by the organism. Several PAHs, PCBs and PCDDs are carcinogenic, while certain phthalate esters can enhance the excretion of zinc, potentially leading to zinc deficiency. Zinc, an essential element, plays a vital role in spermatogenesis and mature T-cell production. Deficiency may result in abnormalities of the male reproductive system, depletion of spermatogenesis and suppression of the immune system. 

For Further Reading J. J. R. Frausto da Silva and R. J. P. Williams, The Biological Chemistry of the Elements The Inorganic Chemistry of Life (Oxford Oxford University Press, 1991). M. F.. Wastney, W. A. House, R. M. Barnes, and K. N. S. Subramanian, "Kinetics of zinc metabolism variation with diet, genetics and disease, Journal of Nutrition, vol. 130, 2000, pp. 1355S-1359S. 

The lack of zinc can also be a problem in biological systems and is responsible for disease states. For example, nitric oxide-dependent apoptosis can be induced in motor neurons by zinc-deficient SOD, and in some cases of amyotrophic lateral sclerosis, zinc-deficient SOD may participate in this type of oxidative mechanism involving nitric oxide.969 One form of hereditary human hair loss or alopecia was mapped to a specific gene and a mutation found in affected individuals. The gene encodes a single zinc finger transcription factor protein with restricted expression in the brain and skin.970 Zinc has been implicated in Alzheimer s via beta amyloid formation, and a role has been attributed for the cerebral zinc metabolism in the neuropathogenesis of Alzheimer s disease.971... 

In some ways it is surprising that aerobic bacteria have not made more use of zinc, internally, and calcium generally, especially in controls since we know they present no redox threat and we shall see that their uses increase dramatically in eukaryotes. The aerobic bacteria do have genetic connections for controlling zinc (e.g. the transcription factor ZUR and ZntR genes) but its use is not extensive. The absence of full use of Ca and Zn may well be due to the limited space and the fast time of the bacterial cell metabolism and life cycle. 

Zinc interacts with numerous chemicals, sometimes producing greatly different patterns of accumulation, metabolism, and toxicity when compared to zinc alone. Recognition of these interactions is essential to the understanding of zinc kinetics in the environment. 

High levels of dietary tin increased zinc loss from rats (Greger 1989). Zinc prevented toxic effects of vanadium (10 mg/kg BW) on bone metabolism of weanling rats (Yamaguchi et al. 1989). 

Concentrations of zinc in tissues of aquatic organisms are usually far in excess of that required for normal metabolism. Much of the excess zinc is bound to macromolecules or present as insoluble metal inclusions in tissues (Eisler 1981, 1984, 1993 USEPA 1987). Diet is the most signihcant source of zinc for aquatic organisms and is substantially more important than uptake from seawater (Eisler 1981, 1984). In general, zinc concentrations in sediments and tissues of aquatic organisms are elevated in the vicinity of smelters and other point sources of zinc, and decrease with increasing distance (Ward et al. 1986 Table 9.4). 

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