ABSTRACT
Carotenoids and Apocarotenoids: Colors with Functions 222
Vitamin A Functions in Animal Physiology 223
Molecular Identification of b,b-Carotene-15,150-mono-oxygenases 226 In Vertebrates Three Different VP14-Homologs Exist 227
Molecular Analyses of the Vitamin A Biosynthetic Pathway in Model
Organism 229
What Can We Learn from Insects? 229
Molecular Analysis of the Vitamin A Biosynthetic Pathway in Vertebrates 231
Conclusions 235
References 236
Elucidating the physiological roles of lipids has long been a major concern in
both biology and medicine. Today, we know that lipids are not only a source
of energy, but are also essential for the growth and development of the organism.
Fat-soluble vitamins and other lipids serve as precursors for ligands that bind to
receptors in the nucleus. These receptors, in response to ligand binding, regulate a
complex network of gene activities (1). To become biologically active, dietary
lipids must first be absorbed by the intestine and transformed by metabolic
enzymes for delivery to their sites of action in the body. The co-ordination of
all these processes involves a large number of binding proteins, transporters,
and metabolizing enzymes, which contribute to lipid homeostasis.
