On the phosphoglucomutase activity in pea cotyledons

Abstract

Phosphoglucomutase (PGM) activity increases in extracts of cotyledons of ungerminated pea seeds during incubation. The process occurs both at 4°C and at 20°C, is pH-dependent and impaired in an atmosphere of nitrogen. If extracts are dialyzed or carefully warmed, a decrease of PGM activity is observed during the subsequent incubation. This phenomenon is also present in extracts of cotyledons of germinating seeds. In extracts of cotyledons of seeds that have germinated for 3 days the increase reaches a maximum in 4 h at 4°C and is followed by a rapid decrease. When extracts of cotyledons from 7-day-old peas are incubated, there is no increase, but only a decrease in their PGM activity. Mixing experiments show that these results are not caused by different concentration of inhibitors or activators of the enzymatic reaction and suggest that the PGM protein may be activated by dialyzable and thermolabile substances acting together. This hypothesis must be considered in the interpretation of the cycloheximide-inhibited increase of PGM activity in cotyledons of germinating peas.