22 SUBCELLULAR PARTICLES 



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DISCUSSION 



R. E. Beyer, A. B. Novikoff, Lars Ernster, Alfred Marshak 



Dr. Beyer: I would like to ask a teleological question, for the physiologist must live 

 with this mistress. What cellular function would you assign to the specific phosphatases 

 and ATPases which you have demonstrated in the bile canaliculi and cell surface? Do 

 you think, for example, that the ATPase is competing with hexokinase for ATP? And 

 what does this mean in terms of cellular function? 



Dr. Novikoff: In the bile canaliculi, one thinks at once of secretion of bile constitu- 

 ents from the cell, but movement of molecules into the cell is not excluded. It is also 

 possible to conceive of the enzyme as being in\'olved in mo\ement of microvilli or 

 similar cell membrane phenomena. On the biochemical level, we are equally ignorant 

 of the enzyme's function. If it functions as an ATPase, then competition for substrate 

 with hexokinase is an interesting possibility. As suggested in the presentation, it is 

 possible that in vivo it is one of the enzymes involved in oxidative phosphorylation. 

 There is as yet too little indication of the enzyme's role, on either the cytological or 

 biochemical level. 



Dr. Ernster: I don't know whether or not the dye used by Dr. Novikoff uncouples 

 oxidative phosphorylation; we do know that certain dyes, such as 2,6-dichlorophenol- 

 indophenol or methylene blue, interfere with mitochondrial phosphorylation, but 

 whether this is due to a disorganization of the mitoclKindrial structure or to a competi- 

 tive type of enzyme-inhibition is not clear. 



Dr. Novikoff: Thank you very much. Dr. Ernster. 



Dr. Marshak: It is true, as Dr. Novikoff has pointed out, that separation and study 

 of cell particulates received its current impetus from Bensley and Hoerr, but this is 

 only for our generation, for Miescher, Brunton and some of their predecessors studied 

 properties of isolated nuclei almost 100 years ago. 



Dr. Novikoff: It is good that Dr. Marshak points to the importance of the predeces- 

 sors, later and early, of Bensley and Hoerr. Even the separation of cytoplasmic particles 

 ('grana') had been used by Otto Warburg some 20 years earlier. However, the first to 

 employ a method essentially like the modern complete cell fractionation were Bensley 

 and Hoerr, and, one should add, Albert Claude. 



