Bacterial organomercury lyase: a protonolytic detoxification catalyst

Abstract

Bacteria became resistant to organomercurials by enzyme-catalyzed protonolytic fragmentation of the C-Hg bond by the enzyme organomercury lyase to hydrocarbon and mercuric ion products. The gene encoding the enzyme has been subcloned, expressed, and the lyase purified to homogeneity and analyzed for specificity and catalytic mechanism. The retention of stereochemistry as endonorbornyl mercurial is converted enzymically in D20 to2endo-D1-norbornane and lack of other detectable radial pathways support an Sr pathway where C-H bond formation and C-Hg cleavage occur in a single transition state.

The First Structurally Authenticated Organomercury(1+) Thioether Complexes − Mercury−Carbon Bond Activation Related to the Mechanism of the Bacterial Enzyme Organomercurial Lyase

“…However, as the water content was the same in all experiments, it was possible to obtain semi-quantitative values to compare the relative re- ϩ and MeHgCl showed no detectable reaction even after 24 h. MeHgCl is known to be resistant towards strong acids; concentrated hydrochloric acid, for example, causes less than 1% protonolysis after 100 min. [58] This is despite the fact that chloride forms a stronger 1:1 MeHg ϩ complex than [9]aneS 3 , as our competition experiments have shown (see above). It therefore seems very likely that the higher coordination number in [MeHg( [9] Hg) value indicates that in solutions of 3, the coordination number of mercury may exceed 2, as already discussed.…”

Mercury pollution: an emerging problem and potential bacterial remediation strategies

“…The second enzyme of this system i.e., mercuric reductase reduces inorganic (Hg 2? ) to metallic (Hg 0 ) form of mercury at the expense of oxidation of NADPH coenzyme (Walsh et al 1987;Murtaza et al 2002b) (Fig. 3).…”

“…Among them, some are toxic to cells and organisms while others are essential components in the biochemical processes going on in the body of living organisms (Walsh et al 1987). Mercury unlike other hazardous organic compounds cannot get converted to a harmless element and as such total amount of extant mercury becomes finite and unchangeable.…”