Fig. 5.

Dependence of SAM on methionine input. When the long-range interactions are present (green curve), the steady state value of SAM increases slowly and linearly as methionine input is increased over a wide range. When the long-range interactions are removed (red curve), the steady state value of SAM increases more rapidly and accelerates when methionine input becomes high. Both curves show the “substrate switch” [41] in which the steady state value of SAM rises modestly at first as methionine input rises but after a certain point rises extremely rapidly