Detoxification mercury compounds

Enzymatic detoxification or modification AGAC antibiotics /(-Lactams Chloramphenicol Erythromycin Tetracyclines Mercury compounds Formaldehyde Modification by acetyltransferases, adenylylases or phosphotransferases Inactivation (/(-lactamases) Inactivation (acetyltransferases) Esterases produce anhydroerythromycin Enzymatic inactivation Inactivation (hydrolases, lyases) Dehydrogenase... 

Many bacteria are resistant to inorganic and organic mercury compounds. Mercuric reductase (MerA) is a key enzyme in the mercury detoxification pathway. MerA catalyzes the NADPH-dependent reduction of Hg to its volatile, uncharged, elemental state (Hg ). MerA is a cytosolic protein that is homologous to GR, but also has a short C-terminal extension and a long N-terminal extension not found in GR. MerA contains three pairs of cysteines one in the C-terminal extension, one in the N-terminal extension, and one in the GR-like region of the protein. The N-terminal domain binds one molecule of mercury and delivers it to the catalytic core of the protein, made up of the GR-like portion and the C-terminal extension, where it is reduced. The disulfide from... 

Robinson, J.B. and O.H. Touvinen. 1984. Mechanisms of microbial resistance and detoxification of mercury and organomercury compounds physiological, biochemical and genetic analysis. Microbiol. Rev. 48 95-124. 

Not all agents can be readily metabolized. The toxic metals lead and mercury are elements that cannot be degraded but must still be removed from the body. Another important mechanism of detoxification is the attachment or binding of another compound to a toxic chemical to make it easier for the kidney to filter the compound out of the blood and excrete it in the urine. A primary purpose of the kidney is to screen the blood for waste products and concentrate them in the urine for excretion, as occurs, for example, with mercury. Caffeine is excreted in the urine at approximately the same concentration as the blood because the kidney cannot concentrate caffeine. Vitamins, however, are readily concentrated and excess quickly eliminated in the urine. 

The one exception is the capacity of some micro-organisms to methylate certain metals, e.g. arsenic, antimony and mercury, probably as a kind of detoxification mechanism. Methylcobal-amin is the only organometallic compound known to have a physiological function in life processes. 

Melnick and Parkin50 reported a functional model for mercury detoxification by organomercurial lyase MerB. The alkyl compound [HgR(Trn Bu)] (R = Me or Et) reacts with phenylthiol (PhSH) yielding [HgSPh(Tm Bu)] and RH. [HgR(W Bu)] exist as linear two-coordinate complexes in the solid state, whereas in solution a rapid equilibrium between [HgR(ic2-Tm Bu)] and [HgR(K3-Tm Bu)] occurs. 

Melnick and Parkin153 reported a functional model for mercury detoxification by organomercurial lyase MerB. The interaction of the alkyl compound [HgR(Tm Bu)] with phenylthiol has been investigated. 

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