Biochemical Properties of Purified Recombinant Human β-Carotene 15,15′-Monooxygenase
Year: 2002
Type: article
Abstract: Beta-carotene 15,15'-monooxygenase (BCO), formerly known as beta-carotene 15,15'-dioxygenase, catalyzes the first step in the synthesis of vitamin A from dietary carotenoids. We have biochemically and enzymologically characterized the purified recombinant human BCO enzyme. A highly active BCO enzyme was expressed and purified to homogeneity from baculovirus-infected Spodoptera frugiperda 9 insect cells. The K(m) and V(max) of the enzyme for beta-carotene were 7 microm and 10 nmol retinal/mg x min, respectively, values that corresponded to a turnover number (k(cat)) of 0.66 min(-1) and a catalytic efficiency (k(cat)/K(m)) of approximately 10(5) m(-1) x min(-1). The enzyme existed as a tetramer in solution, and substrate specificity analyses suggested that at least one unsubstituted beta-ionone ring half-site was imperative for efficient cleavage of the carbon 15,15'-double bond in carotenoid substrates. High levels of BCO mRNA were observed along the whole intestinal tract, in the liver, and in the kidney, whereas lower levels were present in the prostate, testis, ovary, and skeletal muscle. The current data suggest that the human BCO enzyme may, in addition to its well established role in the digestive system, also play a role in peripheral vitamin A synthesis from plasma-borne provitamin A carotenoids.
Source: Journal of Biological Chemistry
Authors: Annika Lindqvist, Stefan Andersson
Institution: The University of Texas Southwestern Medical Center
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1976521385