Figure 1.

The pathway of galactose metabolism [20]. Substances (X_1–5) represent the following metabolites in the paper referenced: X₁, external galactose (GA_E); X₂, internal galactose (GA_I); X₃, galactose 1-phosphate (G1P); X₄, UDP-glucose (U_GL); and X₅, UDP-galactose (U_GA). The reactions are V_TR, transporter of galactose; V_GK, catalyzed by galactokinase; V_GT, catalyzed by galactose-1-phosphate uridyltransferase; V_EP, catalyzed by UDP-galactose 4-epimerase. X₃ is an inhibitor whose rate is given as V_GK. The kinetic equations, systems parameters, and initial conditions of this model are shown in Appendix 1.