A mesophilic bacterial culture producing a novel thermostable alkaline lipase was isolated from oil rich soil sample and identified as Bacillus subtilis EH 37. The lipase was partially purified by ammonium sulfate precipitation and hydrophobic interaction chromatography with 17.8-fold purification and 41.9 U/ml specific activity. The partially purified enzyme exhibited maximum activity at pH 8.0 and at 60°C. It retained 100% of activity at 50°C and 60°C for 60 min. The presence of Ca +2 , Mg +2 , and Zn 2+ exhibited stimulatory effect on lipase activity, whereas Fe +3 and Co +2 reduced its activity. The enzyme retained more than 80% of its initial activity upon exposure to organic solvents, exhibited 107% and 115% activity in the presence of 15% isopropyl alcohol and 30% n-hexane, respectively. The EH 37 lipase also proved to be an efficient catalyst in synthesis of ethyl caprylate in organic solvent, thus providing a concept of application of B. subtilis lipase in non-aqueous catalysis.
Peptidoglycan, a major glycoconjugate in the mycobacterial cell envelope provides strength to resist osmotic stress and plays a pivotal role in maintaining the cellular morphology. Several unique growth stage specific structural alterations occur in its constituent monosaccharides and peptides that allow Mycobacterium to survive nutrient starvation and environmental stress. Here, we discuss the enzymes involved in its intricate biosynthesis that are novel targets for therapeutic intervention and provide an opportunity for potential antibiotic adjuvants. We also revisit the enzymatic steps which are critical for maintaining the equilibrium between peptidoglycan synthesis and hydrolysis during cellular growth and division specifically focused on the importance of cell wall remodelling during "exit from dormancy" in Mycobacterium, a phenomenon with tremendous physiological and therapeutic importance for intervention in mycobacterial infections.
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