Protein Classification according to Solubilities
- Albumin are characterized by being soluble in water and being coagulated on heating. Example are egg albumin, serum albumin, lactalbumin (from milk), and leucosin (from wheat).
- Globumins are insoluble in water, coagulated by heating, soluble in dilute salt solutions and precipitated when the salt often used. Examples are myosinogen (from muscle), edestin (from hemp seed), ovoglobulin (from egg yolk), serum globulin, amandin (from almonds), legumin (from peas), and excelsin (from Brazil nuts).
- Glutelins are insoluble in neutral solvents but soluble in dilute acids and alkalies. Example are glutenin (from wheat) and oryzenin (from corn).
- Alcohol Soluble Proteins (prolamins or gliadins) are soluble in 70 to 80 percent alcohol. Example are gliadin (from wheat), hordain (from barley), and zein (from corn).
- Fibrous Proteins
- Histones are soluble in water and insoluble in dilute ammonia. Solutions of other proteins precipitate histones. The coagulum formed on heating is soluble in dilute acids. Example are globin (from hemoglobin), thymus histone, and scombrone (from mackerel).
- Protamines are polypeptides – a number of amino acids held together – which are less complex than the proteins so far considered, but are still more complex than proteases and peptones. They are soluble in water, are not coagulated by heating, precipitate other proteins from their aqueous solutions (for example, the insuline protamine complex).
Comments