Substrate specificity of a recombinant chicken o-carotene 15,15'-monooxygenase that converts o-carotene into retinal

摘要

The recombinant o-carotene 15,15'-monooxygenase from chicken liver was purified as a single 60 kDa band by His-Trap HP and Resource Q chromatography. It had a molecular mass of 240 kDa by gel filtration indicating the native form to be tetramer. The enzyme converted o-carotene under maximal conditions (pH 8.0 and 37pC) with a k cat of 1.65 minp# and a K m of 26 oM and its conversion yield of o-carotene to retinal was 120% (mol molp#). The enzyme displayed catalytic efficiency and conversion yield for o-carotene, o-cryptoxanthin, o-apo-8'-carotenal, o-apo-4'-carotenal, l-carotene and d-carotene in decreasing order but not for zeaxanthin, lutein, o-apo-12'-carotenal and lycopene, suggesting that the presence of one unsubstituted o-ionone ring in a substrate with a molecular weight greater than C seems to be essential for enzyme activity.