What is the key apolipoprotein involved in the formation of chylomicrons and their secretion into lymphatics?

The key apolipoprotein involved in the formation of chylomicrons and their secretion into the lymphatics is ApoB-48. Chylomicrons are lipoproteins synthesized in the intestinal enterocytes after a meal rich in fats. They are primarily composed of triglycerides, cholesterol, and specific proteins called apolipoproteins.

ApoB-48 is a crucial component as it plays a significant role in the assembly and secretion of chylomicrons. It is synthesized from the mRNA of the ApoB gene but is a truncated form that consists of only part of the ApoB protein compared to ApoB-100, which is found in other lipoproteins like LDL. The presence of ApoB-48 allows the chylomicrons to exit the enterocytes and enter the lymphatic system, where they subsequently enter the bloodstream.

The role of ApoB-48 is essential in the initial steps of lipid transport from the intestine, making it the primary apolipoprotein for chylomicrons. Other apolipoproteins mentioned have their specific functions in lipid metabolism but do not play the same critical role in the formation and secretion of chylomicrons.