Inhibitory effect of the regulatory subunit of type I cAMP-dependent protein kinase on phosphoprotein phosphatase |
| |
Authors: | A K Srivastava R L Khandelwal J L Chiasson A Haman |
| |
Institution: | Clinical Research Institute of Montreal, Quebec, Canada. |
| |
Abstract: | The regulatory subunit of type I cAMP-dependent protein kinase (RI) from rabbit skeletal muscle inhibited the activity of a low molecular weight phosphoprotein phosphatase. The inhibition was concentration and time dependent. A maximum inhibition, about 70%, was observed at 2 microM of RI with an apparent Ki of 0.8 microM. Inhibition was associated with a decrease in Vmax with no change in Km for substrate, phosphorylase a. On the other hand, cAMP-dependent protein kinase holoenzyme or its catalytic subunit was without any effect. The inhibition of phosphoprotein phosphatase by RI may be of physiological significance since the dissociation of cAMP-dependent protein kinase by cAMP would result in a simultaneous increase in the phosphorylation and decrease in the dephosphorylation rates of target proteins. |
| |
Keywords: | |
|
|