Free CDK ( normalized with c0 )c=(c0-x-x1-ix-ixp)/c0.
CKI binding to Active Cyclin:CDK complex
One site phosphorylated CDC25 degradaton
Cyclin:CDK:CKI complex with CKI unphosphorylated
Cyclin:CDK:CKI complex with CKI phosphorylated
Two site phosphorylated CDC25 degradation
This model is from the article: Dynamics of the cell cycle: checkpoints, sizers, and timers. Qu Z, MacLellan WR, Weiss JN Biophys. J. 2003 Dec; 85(6): 3600-11 14645053 , Abstract: We have developed a generic mathematical model of a cell cycle signaling network in higher eukaryotes that can be used to simulate both the G1/S and G2/M transitions. In our model, the positive feedback facilitated by CDC25 and wee1 causes bistability in cyclin-dependent kinase activity, whereas the negative feedback facilitated by SKP2 or anaphase-promoting-complex turns this bistable behavior into limit cycle behavior. The cell cycle checkpoint is a Hopf bifurcation point. These behaviors are coordinated by growth and division to maintain normal cell cycle and size homeostasis. This model successfully reproduces sizer, timer, and the restriction point features of the eukaryotic cell cycle, in addition to other experimental findings. Figure6B has been reproduced by both SBMLodeSolver online and MathSBML. We do not include the synthesis of cyclins is proportional to cell size (Equation 2 in Page3604 of the paper) in this model. The author of the paper keep all the variables and parameters dimensionless. But in the model, we choose to use default units of SBML. This model originates from BioModels Database: A Database of Annotated Published Models. It is copyright (c) 2005-2009 The BioModels Team. For more information see the terms of use . To cite BioModels Database, please use Le Novère N., Bornstein B., Broicher A., Courtot M., Donizelli M., Dharuri H., Li L., Sauro H., Schilstra M., Shapiro B., Snoep J.L., Hucka M. (2006) BioModels Database: A Free, Centralized Database of Curated, Published, Quantitative Kinetic Models of Biochemical and Cellular Systems Nucleic Acids Res., 34: D689-D691.