ENDOGENOUS CATABOLISM 17 



Rahn assumed that the enzymes within the cell behave 

 as they do outside. The deficiency in the cells from 

 enzyme deterioration is made up through the synthesis 

 of new enzyme by the cell itself. The cells have the 

 power to produce enzymes not once only, during growth, 

 but as often as is necessary, to keep the supply normal, 

 as has been shown by many experiments with yeast 

 zymase by Buchner, Buchner and Hahn. 



A certain amount of the cell enzymes thus deteriorates 

 at a constant rate under constant conditions. The 

 deteriorated enzyme, being a waste product, is decom- 

 posed by an autolytic enzyme; perhaps parts of the 

 products are utilized for the synthesis of new enzyme; 

 the rest of the cleavage products leaves the cell. Other 

 unstable cell constituents will have a similar fate, and 

 the total sum of all such deterioration is what we call 

 endogenous catabolism. 



Meyerhof's experiment with the Nitrobacter (see 

 Table 2) is very interesting in this respect. The 

 oxidizing enzyme seems to be very readily deteriorated, 

 and can be rebuilt only from CO2, not from its own 

 cleavage products. 



This chemical interpretation of the wear and tear 

 gives a simpler explanation to the endogenous catabolism 

 of the working muscle. The work of the muscle requires 

 additional energy, i.e., a faster combustion of food in the 

 cells. This combustion is brought about by enzymes 

 in the cells, but it is a well known rule of enzyme action 

 that they do not deteriorate faster when acting than when 

 resting. Whether the muscle works or rests, the rate of 

 enzyme deterioration is not influenced. 



But the rate is greatly influenced by an increase in 

 temperature (see p. 124). As soon as the work of the 

 muscle comes to a point where there is a considerable 



