Characterization of an apo-carotenoid 13,14-dioxygenase from Novosphingobium aromaticivorans that converts β-apo-8'-carotenal to β-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(m) of 21 μM, and k(cat) of 25 l/min. The enzyme exhibited cleavage activity only for carotenoids containing one β-ionone ring and its catalytic efficiency (k(cat)/K(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(13)-C(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.