Proteoglycans

Proteoglycans.— By using a vertical tube rotor for isopycnic centrifugation, the time taken for the isolation of proteoglycans from various tissues can be shortened and the resolution of proteoglycans is improved. Invertebral disc proteoglycans 

Rufini, M. Ghebregzabher, G. Castellucci, and M. Lato, Clin. Chim. Acia, 1979,95,443. 

The use of caesium sulphate as a gradient-forming salt, instead of caesium chloride, to give improved separations of proteoglycans from bovine nasal cartilage has been advocated. The distribution of the link proteins in different proteoglycan extracts may be followed. 

Structural similarities in two major link-proteins from bovine nasal cartilage have been identified after proteolysis and examination of their peptide patterns. The major difference between them is in their carbohydrate contents. 

By using monospecific antisera and immunofluorescence microscopy, proteo- 

A significant number of biopolymers found in animals contain both a protein chain and carbohydrates in the same molecule. These biopolymers are classified as either glycoproteins or proteoglycans. The differentiation of the two classes is based on the number of carbohydrate units per unit length of protein backbone, with the protein predominant in glycoproteins and carbohydrate predominating in proteoglycans. A third 

Glycoproteins will be discussed in some detail in Section 12.4. The carbohydrate components of proteoglycans are known as glycosaminoglycans. Proteoglycans are essential parts of the connective tissue In mammals and are also present to some extent in fish and bacteria (peptidoglycans from the cell wall of bacteria are different biopolymers and were discussed in Section 7.9). The term mucopolysaccharide was used in the past to describe polysaccharide materials of animal origin containing 2-amino-2-deoxyhexoses. 

The proteoglycans are formed from a protein chain, a linkage (carbohydrate) region and a considerably large glycosaminoglycan region, connected as shown below  

Eight main glycosaminoglycans have been identified [62] in proteoglycans and are indicated in Table 7.14.1. 

Different glycosaminoglicans are not very different in structure. For example, the repeating unit in chondroitin is - 4)-0-(p-D-glucopyranosyluronic acid)-(1 3)-0-(2-acetamido-2-deoxy-p-D-galactopyranosyl)-(1 - . The number of units varies but can be in the range of hundreds. Hyaluronic acid has a rather similar structure, - 4)-0-(p-D-glucopyranosyluronic acid)-(1 - 3)-0-(2-acetamido-2-deoxy-p-D-glucopyranosyl)-(1 as shown below  

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Proteoglycans — Biological and Chemical Aspects in Human Life, by J.F. Kennedy... 

Protenoids Proteoglycans Proteolysis Proteolytic enzymes Proteus... 

Glycoconjugates. Another class of carbohydrates are the glycoconjugates (14), composed of glycoproteins, proteoglycans, peptidoglycans, and glycohpids. 

There are other glycosaminoglycans. Hyaluronic acid [9004-61-9] occurs both free and in noncovalent association with proteoglycan molecules. Heparin [9005-49-6] and heparan sulfate [39403-40-2] also known as heparitin sulfate [9050-30-0] occur in mast cells and in the aorta, Hver, and lungs. 

Chymopapain [9001 -90-6] derived from the latex of the papaya tree, produces improvement in lower back pain and sciatica in the majority (75%) of recipients (185—189) when injected into the lumbar intervertebral disks of patients suffering from herniated disk (the nucleus pulposus). This treatment degrades the proteoglycans of the diseased nucleus pulposus, resulting in shrinkage of the disk and reduction of pressure on the nerve roots (190). 

Proteoglycans (from cultured human muscle cells). Separated by ion-exchange HPLC using a Biogel TSK-DEAE 5-PW analytical column. [Harper et al. Anal Biochem 159 150 1986.]... 

A Sail, R Matsumoto, HP McNeil, M Karplus, RL Stevens. Three-dimensional models of four mouse mast cell chymases. Identification of proteoglycan-bmdmg regions and protease-specific antigenic epitopes. I Biol Chem 268 9023-9034, 1933. 

Mucus Viscous glycoprotein, proteoglycan secretion of goblet cells and... 

Structural proteins u-Keratin Collagen Elastin Eibroin Proteoglycans... 

FIGURE 7.33 Glycosamiooglycaos are formed from repeating disaccharide arrays. Glycosamiooglycaos are compooeots of the proteoglycans. 

Lennarz, W. J., 1980. The Biochemistry of Glycoproteins and Proteoglycans. New York Plenum Press. 

Rnoslahti, E., 1989. Proteoglycans in cell regulation. y<9wrn z/ of Biological Chemistry 264 13369—13372. 

Proteoglycans may be soluble and located in the extracellular matrix, as is the case for serglycin, versican, and the cartilage matrix proteoglycan, or they may be integral transmembrane proteins, such as syndecan. Both types of proteoglycan... 

FIGURE 9.31 The known proteoglycans include a variety of structures. The carbohydrate groups of proteoglycans are predominantly glycosaminoglycans O-linked to serine residues. Proteoglycans include both soluble proteins and integral transmembrane proteins. 

Proteoglycan Glycosaminoglycan Protein M, Number of Amino Acid Residues... 

Secreted or extracellular matrix proteoglyeans Large aggregating cartilage proteoglycans CS/KS 220,952 2124... 

FIGURE 9.32 Proteoglycans serve a variety of functions on the cytoplasmic and extracellular surfaces of the plasma membrane. Many of these functions appear to involve the binding of specific proteins to the glycosaminoglycan groups. 

The proteoglycan-hyaluronate aggregates are highly hydrated by virtue of strong interactions between water molecules and the polyanionic complex. 

FIGURE 9.34 Hyaluronate (see Figure 7.33) forms the backbone of proteoglycan structures, such as those found in cartilage. 

Kjellen, L., and Lindahl, U., 1991. Proteoglycans Structures and interactions. Annual Review of Biochemistry 60 443—475. 

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