FRANK H. JOHNSON 



1 



287 



T 



T — r— I — I — I — r 



EXTRACTS. A FISCHERI 



1 — I — I — I — I — I — I — r- 



LIVING CELL^RPHOSPHOREUM _ 



•<* 



J I UJ. 



J I L 



I I I L_ 



2000 4000 



I .L 1 



6000 90 



hy^ 



2000 4000 8000 8000 



PRESSURE (psi) 



Fig. 13. Steady-state levels of luminescence in tlie saturated system of A. fischeri 

 extracts (left) and in living cells of P. phosphoreum (right). The data on the 

 right are replotted from Brown, Johnson, and Marsland (1942). The initial 

 intensity at normal pressure is arbitrarily taken equal to 100 at each tem- 

 perature, and allowance is made for decay, when significant, in the lumi- 

 nescence of extracts. The lower of the two curves for 26° C was obtained 

 with an enzyme solution that had stood for several days at room tempera- 

 ture. (After Strehler and Johnson, 1954.) 



which has ah-eady been expressed, namely, that at these relatively 

 high temperatures, pressure acts to reverse an equilibrium change 

 from native to denatured states of an essential enzyme (or enzymes), 

 thereby increasing the overall velocity of the light-emitting reaction. 

 Qualitative evidence for a reversible thermal denaturation of the 

 extiacted enzyme system was found by visual observation: diminu- 

 tion in intensity occurs on momentary exposures of luminescent solu- 

 tions to relatively high temperatures, followed by recovery on cool- 

 ing. At low temperatures, where the amount of thermally denatured 

 enzyme is negligible, pressure merely reduces the steady-state level. 



