Globulins are proteins found in animal and human organisms. They can be divided into four groups. In addition to alpha-1 globulins, these plasma proteins include alpha-2 globulins, beta globulins, and gamma globulins. Most globulins are formed in the liver, some in plasma cells. They have very different functions in the human body. An increase or decrease in certain globulin levels can therefore indicate a wide variety of diseases. For example, a hereditary disease is the so-called alpha-1 antitrypsin deficiency.
What are globulins?
Globulins are plasma proteins found in animals and humans. They also serve as storage media for plant organisms. Today, more than one hundred plasma proteins are known. They are present in blood plasma at a concentration of about 7.5 grams per deciliter. They are divided into albumins and globulins. Albumins account for the largest proportion of the total protein content at 60 percent, closely followed by the so-called immunoglobulins. Most globulins are formed in the liver. A subset of these proteins, gamma globulins, on the other hand, are released into the blood by plasma cells.
Anatomy and structure
The distinction of proteins into albumins and globulins can be explained by their different properties and solubility behavior. While albumins are soluble in water, globulins are very poorly soluble in water. Globulins can be divided into four groups. The so-called alpha-1 globulins include, for example, the billirubin transporter, transcortin, transcobalmin and alpha-1 antitrypsin. Alpha-2 globulins include plasminogen, alpha-2 macroglobulin, and haptoglobin. Transferrin, C-reactive protein, and lipoproteins belong to the beta-globulin group. The group of immunoglobulins such as IgA and IgE are gamma globulins. Globulins are so-called glycoproteins. These proteins are macromolecules consisting of a protein molecule and one or more sugar groups bound together. Often, these proteins are composed of simple sugars such as glucose, fructose, or mannose.
Function and tasks
The different groups of globulins possess different functions in the human organism. The group of alpha-1 globulins is a rather small group, accounting for only four percent of the total protein content in blood plasma. A special role is played by the so-called Alpa-1 antitrypsin. This protein is a so-called serpin. It protects the body from serine proteases by inhibiting their action. As a result, the protein is prevented from being degraded into cells. The protein acts specifically against the protein-digesting trypsin. Alpha-2 globulins account for about eight percent of the total protein content in blood plasma. Significant in terms of quantity are, for example, haptoglobin and alpha-2-macroglobulin. The latter plays a role in inflammatory processes, but is otherwise clinically insignificant. Haptoglobin is a transport protein for hemoglobin, the red blood pigment. Unbound hemoglobin is toxic and can damage nerve fibers around the kidneys in particular. Therefore, the central task of haptoglobin is to transport the blood pigment to the reticuloendothelial system. There it can be broken down and excreted by the kidneys. Thus, haptoglobin also has an antibacterial effect. While hemoglobin is bound to the protein, it is no longer available as a substrate for microorganisms during infections. Beta-globulins cover 12 percent of the total protein content. An important representative of this group is the globulin transferrin. Transferrin is a transport protein for iron, which has a toxic effect in unbound form. Also important is the so-called fibrinogen. Fibrinogen is responsible for blood clotting. It closes open wounds by forming a fibrin network. The gamma globulins include the so-called immunoglobulins. They cover about 16 percent of the protein content in blood plasma. These globulins are formed in plasma cells and released from there into the blood. An important role is played, for example, by immunoglobulin M. It is responsible for the initial antibody response of the immune system. Immunoglobulin A is secreted primarily as antibodies in body fluids to fight pathogens there.
Diseases
A condition called alpha-1 antitrypsin deficiency is a hereditary disease.In affected individuals, the globulin alpha-1-antitrypsin is not produced correctly in the liver and thus cannot be transported into the bloodstream. As a result, trypsin is no longer inhibited in its function and attacks the body’s cells. This deficiency primarily damages the lungs and liver. An increase or decrease of globulins in the human body can give an indication of various diseases. An increase in alpha-1 globulins can occur, among other things, in acute infections, tissue injuries, rheumatic diseases, heart attacks, inflammatory bowel diseases or tumors. If decreased, liver inflammation may be present in addition to the alpha-1 antitrypsin deficiency already described. Alpha-2-globulins are increased during acute inflammatory phases in the body, but can also occur in connection with kidney diseases. Deficiency of alpha-2-globulin need not have clinical relevance, but may occur in the presence of malnutrition or destruction of red blood cells. An excessively high beta-globulin level may indicate inflammation, liver cirrhosis, iron deficiency, or high cholesterol, among other conditions. A low concentration in the blood can occur with malnutrition. In addition, people suffering from autoimmune diseases may have low beta-globulin levels. If gamma globulin is elevated, there is probably an already prolonged inflammation in the body. In addition, these globulins are produced in breast cancers. A decrease in gamma globulin levels may indicate a congenital disorder of the immune system. In addition, patients may have low gamma globulins after chemotherapy.
