Characterization of esterase activity from an Acetomicrobium hydrogeniformans enzyme with high structural stability in extreme conditions

The biotechnological and industrial uses of thermostable and organic solvent-tolerant enzymes are extensive and the investigation of such enzymes from microbiota present in oil reservoirs is a promising approach. Searching sequence databases for esterases from such microbiota, we have identified in silico a potentially secreted esterase from Acetomicrobium hydrogeniformans, named AhEst. The recombinant enzyme was produced in E. coli to be used in biochemical and biophysical characterization studies. AhEst presented hydrolytic activity on short-acyl-chain p-nitrophenyl ester substrates. AhEst activity was high and stable in temperatures up to 75 °C. Interestingly, high salt concentration induced a significant increase of catalytic activity. AhEst still retained ~ 50% of its activity in 30% concentration of several organic solvents. Synchrotron radiation circular dichroism and fluorescence spectroscopies confirmed that AhEst displays high structural stability in extreme conditions of temperature, salinity, and organic solvents. The enzyme is a good emulsifier agent and is able to partially reverse the wettability of an oil-wet carbonate substrate, making it of potential interest for use in enhanced oil recovery. All the traits observed in AhEst make it an interesting candidate for many industrial applications, such as those in which a significant hydrolytic activity at high temperatures is required

Structure and dynamics of the staphylococcal pyridoxal 5-phosphate synthase complex reveal transient interactions at the enzyme interface

Infectious diseases are a significant cause of death, and recent studies estimate that common bacterial infectious diseases were responsible for 13.6% of all global deaths in 2019. Among the most significant bacterial pathogens is Staphylococcus aureus, accounting for more than 1.1 million deaths worldwide in 2019. Vitamin biosynthesis has been proposed as a promising target for antibacterial therapy. Here, we investigated the biochemical, structural, and dynamic properties of the enzyme complex responsible for vitamin B6 (pyridoxal 5-phosphate, PLP) biosynthesis in S. aureus, which comprises enzymes SaPdx1 and SaPdx2. The crystal structure of the 24-mer complex of SaPdx1-SaPdx2 enzymes indicated that the S. aureus PLP synthase complex forms a highly dynamic assembly with transient interaction between the enzymes. Solution scattering data indicated that SaPdx2 typically binds to SaPdx1 at a substoichiometric ratio. We propose a structure-based view of the PLP synthesis mechanism initiated with the assembly of SaPLP synthase complex that proceeds in a highly dynamic interaction between Pdx1 and Pdx2. This interface interaction can be further explored as a potentially druggable site for the design of new antibiotics