Also found in: Dictionary, Thesaurus, Medical.
a group of animal and plant proteins very widely distributed in nature. Globulins belong to the group of globular proteins. They are soluble in dilute solutions of neutral salts and dilute acids and alkalies but are insoluble in water (with the exception of myosin and several other globulins). They are precipitated in a semi saturated solution of ammonium sulfate, a saturated magnesium sulfate solution (at 30° C), or a saturated sodium sulfate solution (at 37° C). The molecular weights of globulins vary from a few thousand to a million or more. Most globulins are simple proteins, but some (particularly blood serum globulins) are bound to carbohydrates or lipids. The globulin of thyroid iron— thyroglobulin (molecular weight, 630,000)—is the only protein containing iodine. The globulins of nerve tissue—neuroglobulin and neurostromin—are compounds with nucleic acids (nucleoproteins). In relation to both alcohol and temperature, plant globulins (for example, glycinin, edestin, and legumin) are more stable than animal globulins.
Globulins enter into the composition of cytoplasm, blood plasma, and lymph (higher animals and humans), fixing their buffer capacity and the body’s properties of immunity. In addition to globulins, blood plasma contains protein albumins, and the albumin/globulin ratio has diagnostic significance. Normally it is near two, but it falls in inflammatory ailments. Gamma-globulin is used in medicine.