Heparin is a glycosaminoglycan, which is a highly dispersed sulphate polysaccharide with uneven structure.
Low molecular weight heparin is defined in the following two ways:
1. Heparin with molecular weight between 4000 and 6500 daltons has unique anticoagulant properties, which is called low molecular weight heparin. Like ordinary heparin, lmWH-AT complex is formed by binding with antithrombin (AT) to inhibit the activities of thrombin (FA) and coagulation factor XA (FXA)
2. Ordinary heparin used in the past is a mixture of uneven molecular weight, molecular weight of 3000 ~ 57000, molecular weight of heparin below 7000 is called low molecular weight heparin. Low molecular weight heparin can only bind to antithrombin ⅲ, while ordinary heparin can bind to platelets in addition to antithrombin ⅲ, which can inhibit not only the formation of thrombin on platelets surface, but also the aggregation and release of platelets.
Heparin sulfate is a glycoamine polysaccharide widely distributed on the surface of animal cells and extracellular matrix in the form of proteoglycan.
The carboxyl and sulfate groups in heparin molecules, including their content and location, are closely related to their anticoagulant activity. Objective: To investigate the relationship between the anti-tumor metastasis effect of heparin and these components.
Heparin and heparin sulfate. Although they belong to the same category, their distribution, structure and function are quite different. Heparin is produced by mast cells near blood vessels and stored in mast cell granules. It should be released after certain stimulation and has an anticoagulant effect. Heparin sulfate is ubiquitous on various cell surfaces and is involved in membrane structure and cell-matrix interaction. The common structural feature of heparin and heparin sulfate is that eduronic acid or glucuronic acid and acetyl glucosamine form a disaccharide unit, which has a high degree of acidification. However, in heparin there are more iduronic acids than glucuronic acids, and in heparin sulfate they are approximately equal. Compared with heparin, heparin sulfate has lower sulfur degree and higher acetylation degree. Their core proteins are completely different. Heparin is usually present in proteoglycan units.
Heparin has a wide range of molecular weight and its anticoagulant activity is related to its molecular weight. Within a certain range, the affinity of heparin to antithrombin increases with increasing molecular weight because the binding of heparin to antithrombin loses its anticoagulant effect. In addition, the anticoagulant activity of heparin is also related to the carboxyl groups of n-sulfate and uronic acid. Heparan sulfate core protein has a hydrophobic zone on the peptide chain, which can be embedded into the lipid bilayer of the cell membrane and can be used as a structural component of the cell membrane. Glycan and peptides of heparin sulfate exposed on the outer surface of the plasma membrane bind to certain components of the extracellular stroma, such as collagen, fibronectin and laminin, and peptides that extend into the cytoplasm bind to the cytoskeleton, such as actin. Therefore, heparin sulfate not only participates in cell-to-cell and cell-to-matrix interactions, but also transfers information from extracellular to intracellular, with minimal anticoagulant effect.