Inhibitory effect of the regulatory subunit of type I cAMP-dependent protein kinase on phosphoprotein phosphatase.
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.
Srivastava
A K
AK
Clinical Research Institute of Montreal, Quebec, Canada.
Khandelwal
R L
RL
Chiasson
J L
JL
Haman
A
A
D000818:Animals; D007700:Kinetics; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D013696:Temperature; D013997:Time Factors
D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases