390 



/. INHIBITION IN MULTIENZYME SYSTEMS 



changed in various ways (Syrett, 1958). Similar results have been obtained 

 in yeast (Holzer, 1958). The phenomenon of overshoot is clearly seen and 

 in all cases the final steady-state rates are achieved only after circuitous 

 pathways. Such studies, with or without inhibitors, are frequently val- 

 uable in determining whether certain cellular processes are related or 

 not; much more can be found out about this from the variations of these 

 parameters with time than from the final levels reached. 



20- 



INTENSITY 

 OF 



LUMIN 



2Minutes 



TIME 



Fig. 7-42. Example of transition between steady states. The effects of sudden high 

 pressure and the release of this pressiu-e on bioluminescence. A " flash " results from 

 an increase in the pressure and a " blackout " from the drop in the pressure. (From 



Brown et al., 1942.) 



Metabolic Transitions within Cells 



A number of factors may influence transition rates in the complex sys- 

 tem of the cell. Some of these will be mentioned here and they will be taken 

 up in greater detail in the following chapter. We have assumed that the 

 concentrations of the various enzymes in the multienzyme system remain 

 constant in the treatment above, but in the cell this is not necessarily so, 

 since the ability of the enzyme-controlling systems to adapt to changes in 

 substrate concentration is well known. This may lead to very long tran- 



