Characterization of ADP-glucose pyrophosphorylase from shrunken-2 and brittle-2 mutants of maize

Electrophoretic characterization of adenosine diphosphate glucose pyrophosphorylase from the developing endosperms of nine shrunken-2 and four brittle-2 mutants revealed that (1) all mutants had low but detectable levels of activity, (2) mutation at either locus decreased activity of pyrophosphorylases A and B, and (3) differences in mobility were not found. However, pyrophosphorylase B extracted from several shrunken-2 and brittle-2 mutants differed from normal in extent of urea denaturation, K _m (glucose-1-phosphate) or type of glucose-1-phosphate saturation kinetics. Pyrophosphorylase B from sh2-m (association of Dissociation with the sh2 locus) appears to differ from normal in K _m (glucose-1-phosphate).This research was supported by the College of Agricultural and Life Sciences and by National Institutes of Health Grant No. 15422.The investigations reported were included in the thesis submitted by L. C. Hannah to the Graduate School, University of Wisconsin, Madison, Wisconsin, in partial fulfillment of requirement for the Ph.D. degree. Laboratory of Genetics Paper No. 1922.