A
lipoprotein is a biochemical assembly that contains both
proteins and
lipids and may be structural or
catalytic in function. Lipoproteins may be
enzymes,
proton pumps,
ion pumps, or some combination of these functions. Examples include the
high density and
low density lipoproteins of the
blood and the
transmembrane proteins of the
mitochondrion and the
chloroplast.
The lipids are often an essential part of the complex, even if they seem to have no catalytic activity themselves. To isolate transmembrane lipoproteins from their associated membranes, detergents are often needed.