Phosphorylase kinase relies on Ca2+ to exert its activity. Phosphorylase kinase’s sensitivity to Ca2+ is influenced by its activation state and pH. Phosphorylase kinase can be activated by adrenaline[1][2].
Phosphorylase kinase (5 minutes) increases its affinity for Ca2+ after activation [1].
Phosphorylase kinase is inhibited by Ca2+ uptake by the sarcoplasmic reticulum, and this inhibition can be reversed by adding exogenous Ca2+ [1].
References:
[1]. Brostrom CO, et al. The regulation of skeletal muscle phosphorylase kinase by Ca2+. J Biol Chem. 1971 Apr 10;246(7):1961-7.
[2]. Yeaman SJ, et al. The hormonal control of activity of skeletal muscle phosphorylase kinase. Phosphorylation of the enzyme at two sites in vivo in response to adrenalin. Eur J Biochem. 1975 Feb 3;51(1):93-104.