B IO C H E M IS T R Y PE A R L S
Cholesterol can be synthesized in almost all cells, but the liver, intes-
tine, and the steroidogenic tissues such as the adrenal glands and
reproductive tissues are the primary sites.
The major classes of lipoproteins are chylomicrons (lowest density),
very-low-density lipoproteins (VLDLs), intermediate-density
lipoproteins (IDLs), low-density lipoproteins (LDLs), and high-
density lipoproteins (HDLs) (considered the “good cholesterol”).
Familial hyperlipidemia is subdivided into five types, with type V
being most common, characterized by variable elevations of
plasma triglycerides contained predominantly in VLDL.
The rate-limiting step in cholesterol biosynthesis is the enzyme
hydroxymethylglutaryl-CoA reductase (HMG-CoA reductase),
which is the target of the statin drugs.
Berg JM, Tymoczko JL, Stryer L. Biochemistry, 5th ed. New York: Freeman,
Devlin TM, ed. Textbook of Biochemistry with Clinical Correlations, 5th ed.
New York: Wiley-Liss, 2002:742-52.