Biosynthesis, Absorption, and Hepatic Metabolism of Retinol

摘要: Publisher Summary This chapter discusses biosynthesis, absorption, and hepatic metabolism of retinol. The major natural sources vitamin A in the diet are certain plant carotenoid pigments, such as β-carotene, long-chain retinyl esters found animal tissues. β-carotene is converted to A, primarily, intestinal mucosa. biosynthetic process involves two soluble enzymes: 15,15'-dioxygenase retinaldehyde reductase. catalyzes cleavage at central double bond by a dioxygenase mechanism yield molecules retinaldehyde; aldehyde then reduced Dietary hydrolyzed lumen, resulting retinol absorbed into mucosal cell. Retinol cell re-esterified with long-chain, mainly saturated fatty acids; esters, association chylomicrons, transported through lymph general circulation. After entry vascular compartment, chylomicrons metabolized extrahepatic tissues lipolytic removal much chylomicron triglyceride. remnant, thus formed, smaller cholesterol-rich particle that contains essentially all removed from circulation almost entirely liver. uptake hydrolysis re-esterification occur