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The glycolytic enzyme enolase of Staphylococcus aureus is a highly conserved enzyme which binds to human plasminogen thereby aiding the infection process. The cloning, over expression and purification of S. aureus enolase as well as the effect of various metals upon the catalytic activity and structural stability of the enzyme have been reported. The recombinant enzyme (rSaeno) has been purified to homogeneity in abundant amounts (60 mg/L of culture) and the kinetic parameters (Km = 0.23 ± 0.013 × 10−3 M; Vmax = 90.98 ± 0.00052 U/mg) and the optimum pH were calculated. This communication further reports that increasing concentrations of Na+ ions inhibit the enzyme while increasing concentrations of K+ ions were stimulatory. In case of divalent cations, it was found that Mg2+ stimulates the activity of rSaeno while the rest of the divalent cations (Zn2+, Mn2+, Fe2+, Cu2+, Ni2+ and Ca2+) lead to a dose-dependent loss in the activity with a total loss of activity in the presence of Hg2+ and Cr2+. The circular dichroism data indicate that other than Hg2+, Ni2+ and to a certain extent Cu2+, none of the other ions destabilized rSaeno. The inhibitory roles of fluorides, as well as neurotoxic compounds upon the catalytic activity of rSaeno, have also been studied. Conformational changes in rSaeno (induced by ions) were studied using partial trypsin digestion.

In this review, the fish Metallothionein (MT) is broadly discussed in relation to their utilization as a biomarker to assess the heavy metal contamination in marine ecosystem. Heavy metals are the main marine pollutants whose bioaccumulation in fishes results in deleterious effects on physiology, biochemistry and behavior. To assess the health status of fishes, an early determination of metal levels along with a biomarker like MT will help us to understand the bioavailability and toxicity of the metals. MTs constitute a family of low-molecular-weight, cysteine-rich proteins functioning in the regulation of essential metals and detoxification of both essential and nonessential metals. Since 1980, MT has been the useful tool for toxicity assessment of metals before sub lethal and lethal damage to organisms because of quick induction of MTs as metals enter the tissue. Various studies conducted on the induction, regulation and estimation of the MT by the metals showed that many variables such as sexual maturity, age, tissue type, metal type, route of exposure, changes in the environmental conditions of the living habitat of the organisms under study and presence of exogenous and endogenous substances do create fluctuations in the level of MT. Keeping in view of the above factors, this review attempts to understand the effectiveness of this biomarker in assessing the health status of the fishes.Keywords: Biomarker, Heavy Metal, Marine Environment, Metallothionein, Marine Pollution

Infections caused by Staphylococcus aureus are a leading cause of mortality worldwide. S. aureus infections caused by Methicillin-Resistant Staphylococcus aureus (MRSA) are particularly difficult to treat due to their resistance to Next Generation β-lactams (NGB) such as Methicillin, Nafcillin, Oxacillin etc. Resistance to NGBs, which is alternatively known as broad-spectrum β-lactam resistance is classically mediated by PBP2a, a Penicillin-Binding Protein encoded by mecA (or mecC ) in MRSA. Thus, presence of mec genes among S. aureus serves as the predictor of resistance to NGBs and facilitates determination of the proper therapeutic strategy for a staphylococcal infection. Although far less appreciated, mecA deficient S. aureus strains can also exhibit NGB resistance. These strains, which are collectively termed as Methicillin-Resistant Lacking mec (MRLM) are currently being identified in increasing numbers among natural resistant isolates of S. aureus . The mechanism/s through which MRLMs produce resistance to NGBs remains unknown. In this study, we demonstrate that mutations that alter PBP4 and GdpP functions, which are often present among MRLMs can synergistically mediate resistance to NGBs. Furthermore, our results unravel that this novel mechanism potentially enables MRLMs to produce resistance towards NGBs at levels comparable to that of MRSAs. Our study, provides a fresh new perspective about alternative mechanisms of NGBs resistance, challenging our current overall understanding of high-level, broad-spectrum β-lactam resistance in S. aureus . It thus suggests reconsideration of the current approach towards diagnosis and treatment of β-lactam resistant S. aureus infections.