Heavy metals biological functions

Heavy metals with no known biological function, such as aluminum, arsenic, lead, and mercury, are nonessential metals.4-5 These metals are toxic because they can irreversibly bind to enzymes that require metal cofactors. Toxic metals readily bind to sulfhydryl groups of proteins.6-7 In fact,... 

Cadmium occurs naturally as sulfide co-deposited with zinc, copper, and lead sulfides. It is produced as a by-product in above-mentioned metal processing. Similar to lead and mercury, this heavy metal has no known biological functions in living organisms, and accordingly its accumulation in food and water leads to undesirable consequences to biota. Cadmium toxicology is related to dangerous influence to CNS and excretion systems, firstly, on kidney. 

The sorptive nature of bacterial or algal exterior membranes is well-documented [118-122]. Biological particles can influence the distribution of heavy metals in natural waters because the functional groups on the cell surfaces are able to bind certain metal ions [124]. 

Most of our knowledge of the biological effects of petrolemn pollution is based on studying the acute effects of major spills or heavily contaminated sediments. These effects tend to be directly lethal. Acute toxicity has been foimd to be largely related to water solubility, with cmnulative toxicity reflecting the smn of the effects of each individual hydrocarbon. Relatively little is known about the effects of chronic exposures at lower concentrations, especially in the presence of other stressors, such as heavy metals. Effects of chronic inputs from land-based sources on populations, communities, and ecosystem structure and function are also not sufficiently known. 

The heavy metal ions form complexes with proteins, in which carboxylic acid (-COOH), amine (-NH2), and thiol (-SH) groups are involved. These modified biological molecules lose their ability to function properly and... 

Peptides and proteins could be efficient metal binding ligands, because they have the functional groups for metal binding in their amino acid residues, and they can be produced at low cost by recombinant technologies. While many peptides and proteins are known to work as metal transport proteins in biological systems, metallothioneins (cysteine rich proteins with molecular weight of ca. 7 kDa) have attracted researchers attention for decades because they bind heavy metals in vivo [2]. The metallothioneins are considered to be involved in detoxication and metabolism of heavy metals. 

Cobbett CS. Phytochelatin biosynthesis and function in heavy-metal detoxification. Current Opinion in Plant Biology 2000 3(3) 211-216. 

Kandeler, E., Tscherko, D., Bruce, K.D., Stemmer, M., Hobbs, P.J., Bardgett, R.D. and Amelung, W. (2000) Structure and function of the soil microbial community in microhabitats of a heavy metal polluted soil. Biology and Fertility of Soils, 32, 390-400. 

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