Lyase MerB

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. 

In the following sections, some of the approaches and applications described in this article are illustrated using three case studies from our own work. We begin with a mechanistic study of the bacterial organomercurial lyase, MerB, using a quantum chemical cluster method, followed by a QM/MM free energy simulation of the dual-specificity phosphatase, Cdc25B, and a dual QM and QM/MM study of the restriction enzyme EcoRV. 

Case Study 1 Organomercurial Lyase, MerB. In recent work, the mechanism of Hg-C bond cleavage by the bacterial enzyme organomercurial lyase (MerB) was examined using a quantum chemical cluster model (160). 

Microbial demethylations, or dealkylations, of organometallic forms are important reactions in detoxification mechanisms for some metals, such as mercury and tin. Bacterial detoxification of organomercurials is well established and involves the enzyme organomercurial lyase (OL)—a product of the merB gene—that enzymatically cleaves the Hg-C bond to form Hg, which is then reduced by the enzyme mercuric reductase (MR) to the less toxic Hg(0) (Equations (4) and (5)). The high volatility of Hg(0) results in it being rapidly removed to the atmosphere. 

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