- AMP-activated protein kinase phosphorylates R5/PTG, the glycogen targeting subunit of the R5/PTG-protein phosphatase 1 holoenzyme, and accelerates its down-regulation by the laforin-malin complex. Vernia, S., Solaz-Fuster, M.C., Gimeno-Alcañiz, J.V., Rubio, T., García-Haro, L., Foretz, M., de Córdoba, S.R., Sanz, P. J. Biol. Chem. (2009)