Optimized conversion of L-lysine to L-pipecolic acid using recombinant lysine cyclodeaminase from Streptomyces pristinaespiralis

Abstract

Lysine cyclodeaminase (LCD; EC: 4.3.1.28) is a beta-nicotinamide adenine dinucleotide-dependent enzyme that catalyzes the beta-deamination of L-lysine to produce L-pipecolate. L-pipecolate, also known as L-homoproline, is an immunosuppressant and can be incorporated into multiple secondary metabolite products. Recombinant lysine cyclodeaminase from Streptomyces pristinaespiralis (spLCD) has been successfully expressed in E. coli. Among various substrates with different carbon lengths and enantiomeric statuses, L-lysine was found to be the best substrate for spLCD. We also examined the reaction conditions (buffer type, pH and temperature) to yield a high concentration of L-pipecolic acid. Although spLCD was found highly enantioselective toward L-lysine, its enzymatic activity as well as thermostability was seriously decreased under acidic pH conditions and at temperatures higher than 60A degrees C, respectively. A final conversion of L-lysine to L-pipecolate of over 90% was achieved under optimal reaction conditions of 200 mM PIPES buffer, pH 7.0, and a temperature of 60A degrees C