chylomicron synthesis. Dietary triglyceride, phospholipid, and cholesterol, together with intestinally synthesized cholesterol (for which 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase is the rate-limiting enzyme) and recycled biliary cholesterol together with intestinally derived ApoB48 are assembled under the influence of microsomal triglyceride transfer protein (MTP) to form the chylomicron. Prior to incorporation into the chylomicron, cholesterol is esterified by acylcoenzyme A:cholesterol acyltransferase (ACAT) and the triglycerides are reassembled from fatty acids with acylcoenzyme-A-diacylglycerol acyltransferase (DGAT) catalysing the rate-limiting step. The cholesterol is transferred across the membrane by Niemann Pick C1 like-1 and some is reexcreted back into the intestinal lumen by the action of ATP-binding cassette proteins (ABC)G5 and -G8. The particle is assembled under the regulation of microsomal triglyceride transfer protein and delivered to the lymphatics.
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