Characterization of an apo-carotenoid 13,14-dioxygenase from Novosphingobium aromaticivorans that converts [beta]-apo-8'-carotenal to [beta]-apo-13-carotenone

A putative carotenoid oxygenase from Novosphingobium aromaticivorans was purified with a specific activity of 0.8 U/mg by His-Trap affinity chromatography. The native enzyme was estimated to be a 52 kDa monomer. Enzyme activity for β-apo-8'-carotenal was maximal at pH 8.0 and 45 °C, with a half life of 15.3 h, K ^sub m^ of 21 μM, and k ^sub cat^ of 25 l/min. The enzyme exhibited cleavage activity only for carotenoids containing one β-ionone ring and its catalytic efficiency (k ^sub cat^/K ^sub m^) followed the order β-apo-8'-carotenal > β-apo-4'-carotenal > γ-carotene. The enzyme converted these carotenoids to β-apo-13-carotenones by cleaving their C^sub 13^-C^sub 14^ double bonds. The oxygen atom of β-apo-13-carotenone originated not from water but from molecular oxygen. Thus, the enzyme was an apo-carotenoid 13,14-dioxygenase.[PUBLICATION ABSTRACT]