Mechanisms Involved in the Intestinal Digestion and Absorption of Dietary Vitamin A

摘要: Dietary retinyl esters are hydrolyzed in the intestine by pancreatic enzyme, triglyceride lipase (PTL), and intestinal brush border phospholipase B. Recent work on carboxylester (CEL) knockout mouse suggests that CEL may not be involved dietary ester digestion. The possible roles of lipase-related proteins (PLRP) 1 2 other enzymes require further investigation. Unesterified retinol is taken up enterocytes, perhaps involving both diffusion protein-mediated facilitated transport. Once cell, complexed with cellular retinol-binding protein type (CRBP2) complex serves as a substrate for reesterification enzyme lecithin:retinol acyltransferase (LRAT). Retinol bound to CRBP2 esterified acyl-CoA (ARAT). incorporated into chylomicrons, lipoproteins transport lipids such triglycerides, phospholipids, cholesterol. Chylomicrons containing newly absorbed then secreted lymph.