Proteoglycans represent a special class of glycoprotein that are heavily glycosylated. They consist of a core protein with one or more covalently attached glycosaminoglycan chain(s). These glycosaminoglycan chains are long, linear carbohydrate polymers that are negatively charged under physiological conditions, due to the occurrence of sulphate and uronic acid groups. A glycoprotein is a macromolecule composed of a protein and a carbohydrate (a sugar). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Glycosaminoglycans (GAGs) are long unbranched polysaccharides, made up of repeating disaccharides that may be sulphated (e. ...

Types

Proteoglycans can be categorised depending upon the nature of their glycan chains. These chains may be:

• chondroitin sulfate and dermatan sulfate
• heparin and heparan sulfate
• keratan sulfate

Chondroitin sulfate is a glycosaminoglycan found in connective tissue. ... Heparin - Wikipedia, the free encyclopedia /**/ @import /skins-1. ...

Function

Proteoglycans are a major component of the animal extracellular matrix, the 'filler' substance existing between cells in an organism. Here they form large complexes, both to other proteoglycans and also to fibrous matrix proteins (such as collagen). They are also involved in binding cations (such as sodium, potassium and calcium) and water, and also regulating the movement of molecules through the matrix. Evidence also shows they can affect the activity and stability of proteins and signalling molecules within the matrix. Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Subregnum Bilateria  Acoelomorpha  Orthonectida  Rhombozoa  Myxozoa  Superphylum Deuterostomia     Chordata (vertebrates, etc. ... In biology, extracellular matrix (ECM) is any material part of a tissue that is not part of any cell. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, sometimes called the building blocks of life. ... Collagen is the main protein of connective tissue. ... An ion is an atom or group of atoms with a net electric charge. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... Water (from the Old English word wæter; c. ...

Synthesis

The protein component of proteoglycans is synthesised by ribosomes and translocated into the lumen of the rough Endoplasmic Reticulum. Glycosylation of the proteoglycan occurs in the Golgi Apparatus in multiple enzymatic steps, with one sugar unit being added with each step. The completed proteoglycan is then exported in secretory vesicles to the extracellular matrix of the cell. Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... The translocon is the complex of proteins associated with the translocation of nascent polypeptides into the cisternal space of the endoplasmic reticulum. ... The endoplasmic reticulum or ER (endoplasmic means within the cytoplasm, reticulum means little net) is an organelle found in all eukaryotic cells. ... In cell biology, the Golgi apparatus, Golgi body, Golgi complex, or dictyosome is an organelle found in most eukaryotic cells, including those of plants, animals, and fungi. ... Ribbon diagram of the catalytically perfect enzyme TIM. Factor D enzyme crystal prevents the immune system from inappropriately running out of control. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ...

Proteoglycans and Disease

An inability to break down proteoglycans is characteristic of a series of genetic disorders, called mucopolysaccharidoses. The inactivity of specific lysozomal enzymes that normally degraded glycosaminoglycans leads to the accumaltion of proteoglycans within cells. This leads to a variety of disease symptoms, depending upon the type of proteoglycan that is not degraded. A genetic disorder, or genetic disease is a disease caused by abnormal expression of one or more genes in a person causing a clinical phenotype. ... Lysozome could mean: Lysosome Lysozyme This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

Sources

• Functional and Molecular Glycobiology 2002. Brooks SA, Dwek, MV, Schumacher, U. Bios Scientific Publishers.
• Molecular Biology of the Cell (3rd Eddition). Alberts B, Bray D, Lewis J, Raff M, Roberts K, Watson JD. Garland Publishing