Conserved Protein YpmR of Moderately Halophilic Bacillus licheniformis has Hydrolytic Activity on p-Nitrophenyl Laurate

Touray A., OGAN A., TURAN K.

European Journal of Biology, vol.79, no.1, pp.43-50, 2020 (Peer-Reviewed Journal)


Objective: Hydrolases are of great use in many industries including food, textile, paper, detergent, and pharmaceutical production. These enzymes are abundant in all eukaryotic and prokaryotic organisms. Microbial enzymes are relatively tolerant to changes in pH, temperature and salt concentration and are capable of catalyzing reactions with high substrate specificity. Therefore they are potentially important for industrial applications. In this study we aimed to clone and characterize a hypothetically defined moderately Bacillus licheniformis YpmR enzyme, a member of the SGNH-hydrolase superfamily. Materials and Methods: The hypothetical YpmR gene was amplified with PCR using specific oligonucleotide primers and genomic DNA of B. licheniformiss. The purified PCR products were cloned under the control of Escherichia coli lac promoter. Expression of the recombinant YpmR protein in the E. coli cells was assessed using SDS-PAGE/Western blotting. The enzymatic activities were spectrophotometrically determined using p-nitrophenyl laurate (pNPL) and p-nitrophenyl acetate (pNPA). Results: The YpmR enzyme showed a 7-8 fold higher enzymatic activity against the pNPL substrate as compared to the negative controls. Hydrolysis of the pNPL substrate was found to be due to the B. licheniformis YpmR enzyme. In contrast, high hydrolytic activity in bacterial lysates not encoding YpmR enzyme on pNPA substrate indicated that the hydrolysis is due to the presence of other intracellular hydrolases. B. licheniformis YpmR enzyme was shown to be tolerant to high NaCl and Triton X-100 concentration. Conclusion: The moderate halophilic B. licheniformis hypothetical YpmR enzyme heterologously synthesized in E. coli cells has hydrolytic activity on pNPL substrate. The enzyme was observed to be more tolerant to an increase in NaCl and Triton X-100 concentrations compared to the Candida rugosa lipase enzyme used in this study as a control.