Purification and characterization of the surface active proteins of black gram (Phaseolus mungo)

The surface active globulin from black gram has been resolved into two components with high foam-forming activity. They were found to be homogeneous by electrophoresis and ultracentrifugal examinations and had high molecular weights around 100,000 daltons. They were rich in acidic as well basic amino acids but low in sulphur amino acids. Heat treatment, proteolysis and treatment with certain inorganic salts such as copper, and mercurous mercury, group specific reagents P-chloromercury benzoate and N-ethylmalemide (PCMB, NEM) and protein denaturants were found to have an adverse effect, while oxidizing agents had no effect. The free sulphydryl content was low (3 and 4 mumol/mol), but essential for full manifestation of surface activity. Other purified proteins also needed free sulphydryl groups.