Globulin

Globulins are a family of globular proteins that are characterized by their solubility properties. Unlike albumins, which are soluble in pure water, globulins are generally insoluble or only sparingly soluble in pure water but are soluble in dilute salt solutions. They are one of the two major groups of serum proteins, the other being albumins.

Globulins comprise a diverse group of proteins with various functions within the body. They are often classified into three main categories based on their electrophoretic mobility: alpha (α), beta (β), and gamma (γ) globulins.

• Alpha (α) Globulins: This fraction includes proteins such as alpha-1 antitrypsin, alpha-2 macroglobulin, haptoglobin, and ceruloplasmin. These proteins play roles in inflammation, transport, and enzyme inhibition.

• Beta (β) Globulins: This fraction includes proteins such as transferrin (involved in iron transport), complement components (part of the immune system), and lipoproteins (involved in lipid transport).

• Gamma (γ) Globulins: This fraction primarily consists of immunoglobulins (antibodies), which are critical components of the adaptive immune system. Antibodies recognize and bind to specific antigens, marking them for destruction or neutralization. Different classes of immunoglobulins exist, including IgG, IgM, IgA, IgE, and IgD, each with specialized functions.

Globulin levels in the blood can be measured through a serum protein electrophoresis test. Abnormal globulin levels can indicate various medical conditions, including liver disease, kidney disease, autoimmune disorders, infections, and certain types of cancer. Elevated gamma globulin levels, for example, can be indicative of chronic inflammation or infection, or multiple myeloma. Low levels can indicate immunodeficiency.

The term "globulin" can also refer to similar proteins found in plant seeds. These plant globulins serve as storage proteins, providing nutrients for seed germination and seedling growth. Examples include legumin and vicilin found in legumes.