Effective production of retinal from beta-carotene using recombinant mouse beta-carotene 15,15'-monooxygenase

The gene encoding beta-carotene 15,15'-monooxygenase from Mus musculus (house mouse), which cleaves beta-carotene into two molecules of retinal, was cloned and expressed in Escherichia coli. The expressed enzyme was purified by His-tag affinity and resource Q ion exchange chromatography columns to a final specific activity of 0.51 U mg(-1). The optimum pH, temperature, substrate and detergent concentrations, and enzyme amount for effective retinal production were determined to be 9.0, 37 degrees C, 200 mg l(-1) beta-carotene, 5% (w/v) Tween 40, and 0.2 U ml(-1) enzyme, respectively. Under optimum conditions, the recombinant enzyme produced 72 mg l(-1) retinal in a 15-h reaction time, with a conversion yield of 36% (w/w). The specific activity of the purified enzyme and retinal production obtained in the present study were the highest results ever reported.