engleski

Solvent tolerance of halohydrin dehalogenases

Halohydrin dehalogenases catalyze reversible conversion of epoxides to β-haloalcohols in enantioselective fashion with an extensive scope of unnatural nucleophiles.[1] Selectivity and diversity of HHDH enzymes are promising yet insufficient properties to rely solely on them for industrial application purposes. Aqueous solution as physiological medium is the most convenient concerning enzyme natural properties, but poor solubility and hydrolytic instability of hydrophobic substrates make these reactions limited and unfavourable.[2] Thus, biotransformation scale-up often requires modification of the reaction medium by introduction of organic solvents (OSs), which can minimize these problems but also decrease enzyme activity and stability. As a HHDH representative, HheC from Agrobacterium radiobacter AD1 was selected and enzyme activity was determined in the presence of a wide OSs range. Correlation between OSs properties (logP, pKa) and concentration of half-inactivation (C50) was observed. To gain insight into the enzyme behavior in an alternative medium over an extended period of time, activity during incubation with selected OSs was monitored. Besides HheC, we examined the co-solvent stability during incubation of thermostable variant ISM-4. [3] Results obtained reveal that this enzyme is a robust and powerful ally for synthesis in more harsh conditions and a promising candidate for further experimentation in the direction of industrial implementations.

halohydrin dehalogenases ; solvent engineering ; thermostable enzyme variant

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