What is the difference between glycation and glycosylation?
What is the difference between glycation and glycosylation?
Glycation is a non-enzymatic reaction, irreversible and concentration-dependent, in which glucose or other carbohydrates are added onto proteins, lipids or DNA. Glycosylation, on the other hand, is a post-translational process in which the addition of carbohydrates to proteins or lipids is catalysed by enzymes.
What is protein glycation?
Glycation is a reaction in which free amino groups of proteins, lipids, and nucleotides are modified by monosaccharides. During the reaction, a Schiff base, Amadori products, various intermediate compounds, and eventually advanced glycation end products (AGEs) are formed.
What causes protein glycation?
DEFINITION of GLYCATION and AGEs The glycation process is initiated by a chemical reaction between the reactive carbonyl group of a sugar or an aldehyde with a nucleophilic free amino group of a protein, leading to the rapid formation of an unstable Schiff base.
What amino acids are glycated?
The statistical analysis suggests that acidic amino acids, mainly glutamate, and lysine residues catalyze the glycation of nearby lysines. The catalytic acidic amino acids are found mainly C-terminally from the glycation site, whereas the basic lysine residues are found mainly N-terminally.
What are the molecular and clinical consequences of glycation of proteins?
Glycation of cellular proteins produces changes in structure and loss of enzymatic activity. These effects are countered by protein degradation and renewal. This is associated with increased expression of extracellular matrix proteins, vascular adhesion molecules, cytokines, and growth factors.
What is the difference between glycated proteins and glycoproteins?
Glycoproteins are proteins which contain oligosaccharide chains (glycans) covalently attached to amino acid side-chains. Secreted extracellular proteins are often glycosylated. In proteins that have segments extending extracellularly, the extracellular segments are also often glycosylated.
Where does glycosylation of proteins occur?
Golgi apparatus
Glycosylation of proteins and lipids occurs in the endoplasmic reticulum (ER) and Golgi apparatus, with most of the terminal processing occurring in the cis-, medial- and trans-Golgi compartments.
Why is glycosylation of proteins important?
Glycosylation is an important and highly regulated mechanism of secondary protein processing within cells. It plays a critical role in determining protein structure, function and stability. Changes in these complexes result in alterations in how they recruit, interact and activate signaling proteins (e.g. G proteins).
What is glycation and what causes this process?
Glycation is a process which is caused by the presence of excess glucose in skin fibers. This excess triggers an internal reaction in which sugar molecules adhere to the collagen and elastin proteins, which normally help keep skin firm and supple.
What is the glycation theory?
“Glycation” theory suggests that glucose acts as a mediator of aging. Glycation, in which simple sugars (e.g., glucose) bind to molecules such as proteins and lipids, has a profound cumulative effect during life.
What is enzymatic glycation?
Glycation is the most general term describing the adduction of a carbohydrate to another biomolecule, such as a protein, lipid, or DNA. The common term for enzymatic glycation is glycosylation, for example, formation of a glycosidic bond using a sugar nucleotide donor during synthesis of glycoproteins.
Does glucose cause glycation?
What is glycosylation of a protein?
Protein glycosylation is the most common form of posttranslational modification (PTM) on excreted and extracellular membrane-associated proteins (Spiro, 2002). It involves the covalent attachment of many different types of glycans (also called carbohydrates, saccharides, or sugars) to a protein.
What is nonenzymatic protein glycation?
Nonenzymatic protein glycation (glucosylation or glycosylation) by glucose is a complex cascade of reactions yielding a heterogeneous class of compounds, collectively termed advanced glycation end products (AGEs).
How are glycation adducts formed?
Glycation adducts are formed by the reaction of proteins with glucose-reactive α-oxoaldehydes such as glyoxal, methylglyoxal, and 3-deoxyglucosone, and other saccharide derivatives. 6 The initial Schiff base adducts formed from glucose and lysine and N-terminal amino-acid residues rearrange to form fructosamine.
What are the posttranslational modifications in O-linked protein glycosylation?
In O -linked protein glycosylation, posttranslational modifications start in the Golgi with the attachment of a GlcNAc molecule to a serine or threonine residue of a protein. Next, multiple other sugars, such as sialic acid, can be added to the structure. This process is still poorly understood and its elucidation will require further research.
