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Nucleoside Diphosphate Glucose Pyrophosphorylase Isoenzymes of Developing Normal, Brittle-2, and Shrunken-2 Endosperms of Zea mays L.¹

Maize (Zea mays L.) endosperms from normal, brittle-2, and shrunken-2 near-isogenic sublines of the Oh43 inbred were assayed for nucleoside diphosphate glucose pyrophosphorylase activity at 10, 20, and 30 days post-pollination. Polyethaleneamine-cellulose thin layer chromatography and polyacrylamide gel electrophoresis were used for product assay and identification of isoenzyme patterns from crude enzyme preparations, respectively.

Evidence is presented for the existence in corn endosperm of pyrophosphorylose activity with guanosine triphosphate and thymidine triphosphate in addition to adenosine triphosphate, cytidine triphosphate, and uridine triphosphate. Two adenosine diphosphate glucosepyrophosphorylase isoenzyme bands from normal and shrunken-2 endosperms were detected with the same pattern, suggesting that the shrunken-2 gene may be regulatory in nature. Brittle-2 showed an altered mobility of the adenosine diphosphate glucose pyrophosphorylase banding pattern, which indicates that brittle-2 may be a structural gene. Three isoenzymes for uridine diphosphate glucose pyrophosphorylase were found in normal and mutant endosperms. Evidence indicated that guanosine triphosphate may be utilized by adenosine diphosphate glucose pyrophosphorylase. Thymidine triphosphate and possibly cytidine triphosphate may be utilized by uridine diphosphate glucose pyrophosphorylase.

There were no differential appearances of the pyrophosphorylase isoenzymes during corn endosperm development. However, quantitative differences in the isoenzyme bands were observed.

Key Words: Carbohydrate metabolism • Starch biosynthesis

² Formerly Public Health Service Predoctoral Fellow, now Assistant Professor of Agronomy, Professor of Agronomy, and Assistant Professor of Botany and Plant Pathology, respectively, Purdue University, Lafayette, Ind. 47907.

Received for publication January 8, 1972.