. Biochemistry of plants and animals, an introduction. Biochemistry. LIPIDE METABOLISM 461 the amount of this compound picscnt in blood and body tissues. Therefore it is qiute evident that cholesterol must be synthesized in the animal body. Biosynthesis of Cholesterol It has been established that all the carbons of cholesterol synthesized in the animal can be obtained from a common source, acetyl CoA. Although the liver is the site of the majority of cholesterol synthesis in vivo, it has been shown that this compound can be produced by a large variety of tissues. Moreover, many tissues, includ
. Biochemistry of plants and animals, an introduction. Biochemistry. LIPIDE METABOLISM 461 the amount of this compound picscnt in blood and body tissues. Therefore it is qiute evident that cholesterol must be synthesized in the animal body. Biosynthesis of Cholesterol It has been established that all the carbons of cholesterol synthesized in the animal can be obtained from a common source, acetyl CoA. Although the liver is the site of the majority of cholesterol synthesis in vivo, it has been shown that this compound can be produced by a large variety of tissues. Moreover, many tissues, including liver, adrenal cortex, and arterial wall, are capable of stimulating the production of cholesterol iii vitro. The use of such tissues in vitro shows that the cholesterol molecule can also be synthesized from acetoacetic acid, apparently without prior degradation to a C2 unit. Whatever the starting material, acetyl CoA, acetoacetic acid, or isovaleric acid, it is agreed that the formation of cholesterol proceeds through the condensation of acetyl groups to form an isoprenoid unit, which in turn serves as the skeletal material for the production of the hydrocarbon, squalene. Probably the first product of cyclization (ring formation) is lanosterol. At this point the hydroxyl group which ap- CH3COOH \ c—c—c isoprenoid unit (sec page 202). lanosterol squalene. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Mallette, M. Frank (Manney Frank), 1917-. New York, Wiley
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