Discussion 



57 



still a long way from making lysosomes into an obligatory component of 

 the "typical cell". But, at least, there is as yet no evidence to disprove 

 this possibility. I should perhaps add that the capacity to segregate 

 circulating proteins, which may be associated with lysosomes, has been 

 found by Straus (personal communication) to be a property of most 

 tissues. 



Siekevitz : To comment on DPNH cytochrome c reductase : we have 

 been doing experiments with liver microsomes and liver mitochondria 

 containing these enzymes. We can solubilize the enzymes from the 

 microsomes and the mitochondria in the same way with deoxycholate. 

 As I have shown before, the microsomal enzyme can be resedimented if 

 we dilute out the detergent, but the mitochondrial enzyme does not 

 come down after this dilution. There is thus quite a different structural 

 relationship involved between the DPNH reductases of the mito- 

 chondria and of the microsomes. 



