AMP-activated protein kinase: an ultrasensitive system for monitoring cellular energy charge.
The AMP-activated protein kinase cascade is activated by elevation of AMP and depression of ATP when cellular energy charge is compromised, leading to inhibition of anabolic pathways and activation of catabolic pathways. Here we show that the system responds in intact cells in an ultrasensitive manner over a critical range of nucleotide concentrations, in that only a 6-fold increase in activating nucleotide is required in order for the maximal activity of the kinase to progress from 10% to 90%, equivalent to a co-operative system with a Hill coefficient (h) of 2.5. Modelling suggests that this sensitivity arises from two features of the system: (i) AMP acts at multiple steps in the cascade (multistep sensitivity); and (ii) the upstream kinase is initially saturated with the downstream kinase (zero-order ultrasensitivity).
Hardie
D G
DG
Biochemistry Department, Dundee University, MSI/WTB Complex, Dow Street, Dundee DD1 5EH, Scotland, UK. d.g.hardie@dundee.ac.uk
Salt
I P
IP
Hawley
S A
SA
Davies
S P
SP
D055372:AMP-Activated Protein Kinases; D000595:Amino Acid Sequence; D002460:Cell Line; D004734:Energy Metabolism; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012680:Sensitivity and Specificity
D009097:Multienzyme Complexes; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases