Glycation (sometimes called non-enzymatic glycosylation) is the
result of typically covalent bonding of a protein or lipid
molecule with a sugar molecule, such as fructose or glucose,
without the controlling action of an enzyme. All blood sugars
are reducing molecules. Glycation may occur either inside the
body (endogenous glycation) or outside the body (exogenous
glycation). Enzyme-controlled addition of sugars to protein or
lipid molecules is termed glycosylation; glycation is a
haphazard process that impairs the functioning of biomolecules,
whereas glycosylation occurs at defined sites on the target
molecule and is required in order for the molecule to function.
Much of the early laboratory research work on fructose
glycations used inaccurate assay techniques that led to drastic
underestimation of the importance of fructose in glycation.
Exogenous, meaning outside the body, may also be referred to as
dietary or pre-formed. Exogenous glycations and Advanced
Glycation Endproducts (AGEs) are formed when sugar