BCO2:Fe2+ cleaves betaC to APO10al and bION

Beta,beta-carotene 9',10'-oxygenase (BCO2) is able to eccentrically cleave carotenoids to produce long chain (>C20) apocarotenoids (Amengual et al. 2011). This is in contrast to the other provitamin A-converting enzyme, BCMO1 which is able to symmetrically cleave carotenoids to produce apocarotenoids of C20 length, such as all-trans-retinal (atRAL). BCMO1 is the main enzyme involved in retinoid homeostasis and resides in the cytosol whereas BCO2 resides in the mitchondrion, has broad substrate activity and is proposed to provide an alternative, minor route for retinoid production. How apocarotenoids produced by BCO2 cleavage are utilised is the subject of further investigation (Amengual et al. 2013). Being in the mitochondrion, BCO2 is able to degrade carotenoids which, if otherwise allowed to accumulate, are implicated in oxidative damage to the cell (Amengual et al. 2011). In this example, beta-carotene (betaC) is cleaved by BCO2 to produce beta-apo-10'-carotenal (APO10al) and beta-ionone (bION) in an enterocyte cell. Carotenoids, such as betaC, can also be metabolised in many other cell types including hepatocytes and stellate cells of the liver.

β-胡萝卜素9',10'-氧化酶（BCO2）能够非对称性地切割类胡萝卜素，生成长链（>C20）的开环类胡萝卜素（Amengual等，2011年）。此过程与另一类维生素A转化酶BCMO1不同，BCMO1能够对称性地切割类胡萝卜素，生成C20长度的开环类胡萝卜素，例如全反式视黄醛（atRAL）。BCMO1是参与视黄醇稳态的主要酶，存在于细胞质中，而BCO2则位于线粒体中，具有广泛的底物活性，并被提议为视黄醇生产的一种替代的次要途径。由BCO2切割产生的前胡萝卜素如何被利用，是进一步研究的主题（Amengual等，2013年）。由于BCO2位于线粒体中，它能够降解类胡萝卜素，否则这些类胡萝卜素会积累，导致细胞氧化损伤（Amengual等，2011年）。在本例中，β-胡萝卜素（betaC）被BCO2切割，在肠上皮细胞中生成β-开环-10'-胡萝卜醛（APO10al）和β-香叶醛（bION）。类胡萝卜素，如betaC，还可以在许多其他细胞类型中代谢，包括肝细胞和肝脏星状细胞。