globulin(redirected from Thyroxine-binding globulin)
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globulin,any of a large family of proteinsprotein,
any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight.
..... Click the link for more information. of a spherical or globular shape that are widely distributed throughout the plant and animal kingdoms. Many of them have been prepared in pure crystalline form. The term globulin is a partly procedural one, used in classifying an otherwise diverse group of proteins that are soluble in water or dilute salt solutions. Among the most important are the immunoglobulins (Ig), the antibodies of the immune system (see immunityimmunity,
ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity.
..... Click the link for more information. ). They are classified into five types based upon structure: IgA, IgD, IgE, IgG, and IgM. IgG or &ggr;-globulin is the most common and forms about 70% of the immunoglobins in the blood. Other globulins are involved in the transport of a variety of substances, including lipidslipids,
a broad class of organic products found in living systems. Most are insoluble in water but soluble in nonpolar solvents. The definition excludes the mineral oils and other petroleum products obtained from fossil material.
..... Click the link for more information. , hormoneshormone,
secretory substance carried from one gland or organ of the body via the bloodstream to more or less specific tissues, where it exerts some influence upon the metabolism of the target tissue.
..... Click the link for more information. , and inorganic ions.
The introduction of electrophoresis during the 1930s permitted subdivision of the globulins into alpha, beta, and gamma globulins on the basis of relative mobility at alkaline pH (8.6). However, each of these subgroups, though electrophoretically homogeneous, consists of a great variety of proteins with different biological properties and markedly different sizes and chemical properties other than net charge. Thus the α2-globulins, for example, as defined by moving boundary or paper electrophoresis, contain proteins ranging in molecular weight from approximately 50,000 to approximately 1,000,000 (α2-macroglobulin), each with differing functions. See Immunoglobulin