Abstract
Overall scheme of the REC, TEC and TREC values using emulsified state with TC4 or olive oil, or in the form of monomolecular films spread at the air/water interface at low or high interfacial tensions.
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► Negative effect of heterologous expression and N-terminal His-tagging on catalysis. ► Negative effects of REC and TREC are cumulative. ► REC and TEC increase with the decrease of the interfacial tension of the substrate.
The interfacial and kinetic properties of wild type, untagged recombinant and tagged recombinant forms of three staphylococcal lipases (SSL, SXL and SAL3) were compared using the monomolecular film technique. A kinetic study on the dependence of the stereoselectivity of these nine lipase forms on the surface pressure was performed using the three dicaprin isomers spread in the form of monomolecular films at the air–water interface.
New parameters, termed Recombinant expression Effects on Catalysis (REC), N-Tag Effects on Catalysis (TEC), and N-Tag and Recombinant expression Effects on Catalysis (TREC), were introduced.
The findings obtained showed that with all the lipases tested, the recombinant expression process and the N-terminal His-tag slightly affect the sn-1 preference for dicaprin enantiomers as well as the penetration capacity into monomolecular films of phosphatidylcholine but significantly decrease the catalytic rate of hydrolysis of three dicaprin isomers. This rate reduction is more pronounced at high surface pressures, i.e. at low interfacial energies. In conclusion, the effects of the heterologous expression process on the catalytic properties of the staphylococcal lipases are three times more deleterious than the presence of an N-terminal tag extension. In the case of the situation most commonly encountered in the literature, i.e. the heterologous expression of a tagged lipase, the rate of catalysis can be decreased by these processes by 42–83% on average in comparison with the values measured with the corresponding wild type form.