Bco2, or β-carotene oxygenase 2, is an enzyme that converts carotenoids into more polar metabolites, playing a key role in carotenoid metabolism and homeostasis [3]. It is involved in the pathway for vitamin A production and is associated with various biological processes related to carotenoid-dependent functions, such as skin pigmentation and tissue-specific accumulation of carotenoids [2,4]. Genetic models, especially gene-knockout (KO) mouse models, are valuable for studying its function.

In KO mouse models, genetic deletion of Bco2 led to enhanced accumulation of zeaxanthin, indicating that Bco2 serves as a gatekeeper of zeaxanthin bioavailability [1]. In chickens, variations in the BCO2 coding sequence were associated with differences in carotenoid concentration in the skin, influencing skin color [2]. In rainbow trout, miR-330 targeting BCO2 was involved in regulating skin pigmentation [4]. In rabbits, the BCO2 genotype affected the expression of genes related to carotenoid, retinol, and α-tocopherol metabolism [5,6]. In chickens, the domestic BCO2 allele was associated with carotenoid accumulation in certain tissues and the ability to allocate stored carotenoids to eggs, potentially buffering low-carotenoid diets [7].

In conclusion, Bco2 is crucial in carotenoid metabolism, influencing carotenoid bioavailability, tissue accumulation, and pigmentation in various species. Studies using KO mouse models and other animal models have provided insights into its role in these biological processes, which may have implications for understanding carotenoid-related health aspects in humans, such as macular pigment metabolism and potential links to eye health [8].

References:

1. Thomas, Linda D, Ramkumar, Srinivasagan, Golczak, Marcin, von Lintig, Johannes. 2023. Genetic deletion of Bco2 and Isx establishes a golden mouse model for carotenoid research. In Molecular metabolism, 73, 101742. doi:10.1016/j.molmet.2023.101742. https://pubmed.ncbi.nlm.nih.gov/37225015/

2. Wang, Yan, Gan, Shiyi, Luo, Chenglong, Shu, Dingming, Qu, Hao. 2023. Variations in BCO2 Coding Sequence Causing a Difference in Carotenoid Concentration in the Skin of Chinese Indigenous Chicken. In Genes, 14, . doi:10.3390/genes14030671. https://pubmed.ncbi.nlm.nih.gov/36980942/

3. Thomas, Linda D, Bandara, Sepalika, Parmar, Vipulkumar M, Kiser, Philip D, von Lintig, Johannes. 2020. The human mitochondrial enzyme BCO2 exhibits catalytic activity toward carotenoids and apocarotenoids. In The Journal of biological chemistry, 295, 15553-15565. doi:10.1074/jbc.RA120.015515. https://pubmed.ncbi.nlm.nih.gov/32873706/

4. Wu, Shenji, Zhao, Lu, Huang, Jinqiang, Liu, Zhe, Zhang, Dongqiang. 2023. miR-330 targeting BCO2 is involved in carotenoid metabolism to regulate skin pigmentation in rainbow trout (Oncorhynchus mykiss). In BMC genomics, 24, 124. doi:10.1186/s12864-023-09173-z. https://pubmed.ncbi.nlm.nih.gov/36927381/

5. Strychalski, Janusz, Gugołek, Andrzej, Antoszkiewicz, Zofia, Król-Grzymała, Angelika, Matusevičius, Paulius. 2022. The Effect of the BCO2 Genotype on the Expression of Genes Related to Carotenoid, Retinol, and α-Tocopherol Metabolism in Rabbits Fed a Diet with Aztec Marigold Flower Extract. In International journal of molecular sciences, 23, . doi:10.3390/ijms231810552. https://pubmed.ncbi.nlm.nih.gov/36142463/

6. Strychalski, Janusz, Gugołek, Andrzej, Kaczorek-Łukowska, Edyta, Antoszkiewicz, Zofia, Matusevičius, Paulius. 2023. The BCO2 Genotype and the Expression of BCO1, BCO2, LRAT, and TTPA Genes in the Adipose Tissue and Brain of Rabbits Fed a Diet with Marigold Flower Extract. In International journal of molecular sciences, 24, . doi:10.3390/ijms24032304. https://pubmed.ncbi.nlm.nih.gov/36768627/

7. Fallahshahroudi, Amir, Sorato, Enrico, Altimiras, Jordi, Jensen, Per. 2019. The Domestic BCO2 Allele Buffers Low-Carotenoid Diets in Chickens: Possible Fitness Increase Through Species Hybridization. In Genetics, 212, 1445-1452. doi:10.1534/genetics.119.302258. https://pubmed.ncbi.nlm.nih.gov/31160321/

8. Shen, Chou, Bandara, Sepalika, Imanishi, Sanae S, Imanishi, Yoshikazu, von Lintig, Johannes. 2025. Unveiling BCO2 function in macular pigment metabolism: Mitochondrial processing and expression in the primate retina. In Biochimica et biophysica acta. Molecular and cell biology of lipids, 1870, 159600. doi:10.1016/j.bbalip.2025.159600. https://pubmed.ncbi.nlm.nih.gov/39978586/