Glycogen metabolism: the integrated cellular response to a bi-directional metabolic stimulus
Saugmann, P.; Esmann, V.
Biochemical and Biophysical Research Communications 74(4): 1520-1527
1977
ISSN/ISBN: 0006-291X PMID: 402920 Document Number: 117847
The control exerted by phosphorylase a over the I-conversion of glycogen synthase does not apply to glycogen synthesis, as judged from experiments with intact human leukocytes. In incubated leukocytes conversion of glycogen synthase (GS) (EC 2.4.1.11) to GS-I is preceeded by inactivation of glycogen phosphorylase a (GPh-a). By the addition of latex particles a flash-activation of GPh-a can be elicited within 10-30 s in the intact cells. GPh is inactivated when a glucose load is given. When, in glycogen depleted cells, glucose is given immediately after latex the I-conversion of GS is completely abolished, and GS-I remains low for 20 min although GPh is rapidly inactivated after the glucose is given. Glycogen synthesis as compared with a control in which only glucose is given, and in which a large I-conversion occurs, is not the least depressed. This apparent contradiction is completely resolved taking into account a newly discovered, intermediate form of GS (GS-R). An important physiological role can be proposed for GS-R.