General Principles of Biochemistry of the Elements

Copper-Induced Inhibition of Growth of Desulfovibrio desulfuricans G20: Assessment of Its Toxicity and Correlation with Those of Zinc and Lead

“…Cu(II) at toxic concentrations is known to bind to free thiols (e.g., glutathione) and other functional groups (e.g., -SH) of enzymes and may also replace metals that are constituents and the active centers of enzymes, cofactors, or other biomolecules. This results in denaturation and inactivation of enzymes and disruption of cell organelle membrane integrity and cell division (21,36,48,53 The results of this study clearly show that heavy metal toxicity to the sulfate-reducing bacterium D. desulfuricans G20 was demonstrated by inhibition in total cell protein, longer lag times, lower maximum specific growth rates, and in some cases no measurable growth. When the toxicities of Pb(II) and Zn(II) were studied, however, no inhibition in the final cell protein concentration was observed.…”

“…Toxic effects include ion displacement and/or substitution of essential ions from cellular sites and blocking of functional groups of important molecules, e.g., enzymes, polynucleotides, and essential nutrient transport systems (35). This results in denaturation and inactivation of enzymes and disruption of cell organelle membrane integrity (21,36). Microorganisms require some metals like Cu(II), Zn(II), Co(II), and Ni(II) at low concentrations as essential micronutrients for vital cofactors for metalloproteins and certain enzymes (21,35).…”

Is the first enzyme of the shikimate pathway, 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (tyrosine sensitive), a copper metalloenzyme?

“…In our hands, however, the 350-nm-absorbing band of the Cu(II) enzyme was unaffected by the addition of erythrose 4-phosphate (even to levels twice those of phosphoenolpyruvate and even after 1 h at room temperature). We is so rarely used as an electrophilic catalyst (as distinct from a redox center) in enzyme systems, considering the fact that it is preeminent as an acid-base catalyst in model reactions (16) and heads the Irving-Williams series (17). Perhaps Zn(II) is so often preferred because it lacks any redox properties that could complicate the reactions of electron-rich substrates, or perhaps Cu(II) came to be used only relatively late in evolution (16).…”

Enumeration and Characterization of Iron(III)-ReducingMicrobial Communities from Acidic Subsurface Sediments ContaminatedwithUranium(VI)

“…2). In addition to nitrate, the washing step likely removed other toxic metals in solution, thus preventing effects such as pathway blockage, substitution of metals for other functional units, and disturbance of membrane integrity or enzyme function (50,63). Therefore, the numbers of iron(III)-reducing bacteria detected in washed sediment enrichments from the contaminated site could be overestimations of actual in situ potential.…”