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The globulins are a family of
Globulin proteins exist not only in other animal species, but also in plants. Vicilin and legumin, from peas and other legumes, function as protein storage within seeds. These proteins can cause allergic reactions if they bind with human IgE antibodies.
globular protein
In biochemistry, globular proteins or spheroproteins are spherical ("globe-like") proteins and are one of the common protein types (the others being fibrous, disordered and membrane proteins). Globular proteins are somewhat water-soluble (for ...
s that have higher molecular weight
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...
s than albumins
Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins ...
and are insoluble in pure water but dissolve in dilute salt solutions. Some globulins are produced in the liver, while others are made by the immune system. Globulins, albumins
Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins ...
, and fibrinogen
Fibrinogen (factor I) is a glycoprotein complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted enzymatically by thrombin to fibrin and then to a fibrin-based blood cl ...
are the major blood protein
Blood-proteins, also termed plasma proteins, are proteins present in blood plasma. They serve many different functions, including transport of lipids, hormones, vitamins and minerals in activity and functioning of the immune system. Other blood pr ...
s. The normal concentration of globulins in human blood is about 2.6-3.5 g/dL.
The term "globulin" is sometimes used synonymously with "globular protein". However, albumins are also globular proteins, but are ''not'' globulins. All other serum globular proteins are globulins.
Types of globulins
All globulins fall into one of the following three categories : *Alpha globulins
Alpha globulins are a group of globular proteins in plasma that are highly mobile in alkaline or electrically charged solutions. They inhibit certain blood proteases and show significant inhibitor activity.
The alpha globulins typically have mo ...
* Beta globulins
Beta globulins are a group of globular proteins in plasma that are more mobile in alkaline or electrically charged solutions than gamma globulins, but less mobile than alpha globulins.
Examples of beta globulins include:
* beta-2 microglobulin
...
* Gamma globulins
Gamma globulins are a class of globulins, identified by their position after serum protein electrophoresis. The most significant gamma globulins are immunoglobulins (antibodies), although some immunoglobulins are not gamma globulins, and some g ...
(one group of gamma globulins is the immunoglobulin
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of th ...
s, which are also known as "antibodies")
Globulins can be distinguished from one another using serum protein electrophoresis.
Globulins exert oncotic pressure. Their deficiency results in loss of carrier functions of globulins, oedema due to decreased oncotic pressure, and susceptibility to infections due to decreased gamma-globulins (immuno-globulins) leading to decreased production of antibodies.
Sizes ~ weights
Globulins exist in various sizes. The lightest globulins are the alpha globulins, which typically have molecular weights of around 93 kDa, while the heaviest class of globulins are the gamma globulins, which typically weigh about 1193 kDa. Being the heaviest, the gamma globulins are among the slowest to segregate in gel electrophoresis. The immunologically active gamma globulins are also called "immunoglobulin
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of th ...
s" or "antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of ...
".
Human blood plasma levels
The normal concentration of globulins in human blood is about 2.6-4.6 g/dL.
Nonhuman globulins
Globulin proteins exist not only in other animal species, but also in plants. Vicilin and legumin, from peas and other legumes, function as protein storage within seeds. These proteins can cause allergic reactions if they bind with human IgE antibodies.
Pseudoglobulins and euglobulins
Pseudoglobulins are a class of globulins that are more soluble in ammonium sulfate than euglobulins. Pseudoglobulins are also soluble in purewater
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
, while euglobulins are not.
References
External links
* Blood proteins {{protein-stub