Failure to detect UDP-glucose phosphorylase in the developing endosperm of maize and wheat

Abstract

Unfractionated extracts, desalted extracts, and the material precipitated by 60%-saturated (NH 4) 2SO 4 were prepared from the endosperm of developing grains of maize ( Zea mays L.) and wheat ( Triticum aestivum L.). UDP-glucose phosphorylase activity in each type of extract was assayed by measuring, enzymically and radiochemically, production of glucose 1-phosphate from UDP-glucose in the presence of phosphate. No significant activity was detected, nor was any found when ADP-glucose was substituted for UDP-glucose. The view that UDP-glucose phosphorylase plays a significant role in grain filling is questioned.