Thermally stable para-nitrobenzyl esterases

摘要

A method for isolating and identifying modified para-nitrobenzyl esterases which exhibit improved thermal stability relative to naturally occurring para-nitrobenzyl esterase. The method involves preparing a library of modified para-nitrobenzyl esterase nucleic acid segments (genes) which have nucleotide sequences that differ from the nucleic acid segment which encodes for naturally occurring para-nitrobenzyl esterase. The library of modified para-nitrobenzyl nucleic acid segments is expressed to provide a plurality of modified enzymes. The clones expressing modified enzymes are then screened to identify which enzymes retain esterase activity after heat treatment at elevated temperature. Specific modified para-nitrobenzyl esterases are disclosed which have improved thermal stability and/or ester hydrolysis activity in aqueous or aqueous-organic media relative to the thermal stability and/or ester hydrolysis activity of unmodified naturally occurring para-nitrobenzyl esterase.