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Purification and Properties of Adenosine Diphosphoglucose Pyrophosphorylase from Sweet Corn ¹

^a Department of Horticulture, Purdue University, Lafayette, Indiana 47907

A 40-fold purification of adenosine diphosphoglucose pyrophosphorylase from sweet corn (Zea mays var. Golden Beauty) revealed the enzyme to be specific for adenosine triphosphate. The enzyme has an absolute requirement for Mg²⁺ and is activated by 3-phosphoglycerate and to a lesser extent by ribose-5-phosphate and fructose-6-phosphate. The apparent Km values of the enzyme for glucose-1-phosphate, adenosine triphosphate, pyrophosphate, and adenosine diphosphoglucose are 1.9 x 10^–4, 3.2 x 10^–5, 3.3 x 10^–5, and 6.2 x 10^–4M, respectively. Pyrophosphate inhibits adenosine diphosphoglucose synthesis competitively (Ki = 3.8 x 10^–7M), while orthophosphate and sulfate appear to inhibit the reacion noncompetitively. These results show that the production of this sugar nucleotide can be controlled by the concentration of pyrophosphate.

¹ This research was supported by a contract from General Foods Incorporation, Technical Center, White Plains, N. Y. This report is Journal Paper 4521 of the Purdue Agriculture Experiment Station.