Fig. 4

Steady state changes in substrate concentration and fraction transsulfurated when one velocity is knocked out or upregulated. Panel a shows the percentage changes in SAM, GNMT-5mTHF, and 5mTHF concentrations, and fraction transsulfurated in the model when either PEMT, GAMT, or GNMT is knocked out, or when DNMT is 20-fold upregulated. The long-range interactions cause substantial changes in all four variables and these changes are what make the velocity changes in Panel a of Fig. 3 relatively modest. Panel b shows what happens when the long-range interactions are turned off. The GNMT-5mTHF, 5mTHF concentrations, and fraction transsulfurated don’t change at all (except in the case of GNMT knockout), but SAM undergoes enormous changes