STRUCTURAL AND FUNCTIONAL-PROPERTIES OF A PARTIALLY PURIFIED COWPEA (VIGNA-UNGUICULATA) GLOBULIN MODIFIED WITH PROTEIN-KINASE AND GLYCOPEPTIDASE

The major globulin fraction in cowpea seed was partially purified by s elective ammonium sulfate precipitation and gel chromatography. The pa rtially purified protein was enzymatically phosphorylated or deglycosy lated. Phosphate content increased from 5.81 mu g/mg in the untreated protein to 10.55 mu g/mg in the protein kinase treated protein. Fluore scence intensity and protein solubility were significantly (p less tha n or equal to 0.05) increased at pH 3-8 as a result of phosphorylation , while susceptibility to heat-induced coagulation was significantly ( p less than or equal to 0.05) decreased. At 50% deglycosylation, fluor escence intensity was significantly (p less than or equal to 0.05) hig her for the untreated protein than the treated protein. The intensity of the near-UV circular dichroism spectra of the deglycosylated protei n was lower than that of the untreated protein at pH 3, 4, and 6, wher eas the reverse was observed at pH 7 and 8. The deglycosylated protein was less soluble at pH 3, 4, 7, and 8 and was more susceptible to hea t coagulation when compared to the untreated protein. Modification by protein kinase would allow use in foods where greater solubility is ne eded, while deglycosylation could enhance utilization in foods that re quire heat-induced coagulation.