Cytoplasmic & Nuclear Structure & Metabolism 11 



instance, show a very slow decrease in the non-nucleated 

 halves; a third group, including esterase and acid phos- 

 phatase, have practically disappeared from non-nucleated 

 cytoplasm after a few days. This establishes without any 

 doubt that different enzymes are to different extents under 

 nuclear control and that this postulated "control" from the 

 nucleus is much more complex than was expected at first. 



It is still too early to state definitely why the various 

 enzymes we studied behave so differently after removal of the 

 nucleus; a likely explanation, though lacking formal proof as 

 yet, might be the different cytological localizations of these 

 enzymes; as shown by Holter and Lovtrup (1949), in the 

 amoeba, amylase and protease are bound to large mito- 

 chondrion-like particles. This would imply that mitochondria 

 are, by and large, independent of the nucleus. This is, 

 moreover, in perfect agreement with the finding, reported 

 above, that removal of the nucleus has little effect on the rate 

 of cellular oxidations. According to Holter and Pollock (1952), 

 dipeptidase is found in solution in the hyaloplasm; it is there- 

 fore not surprising that it should behave, after removal of the 

 nucleus, like the whole of the proteins of the organism. 

 Finally, acid phosphatase and esterase both show a striking 

 decrease in activity in non-nucleated cytoplasm, just like 

 RNA; it is not unlikely, therefore, that we are here dealing 

 with microsome-bound enzymes. If this proves to be the 

 case, it would mean that these small cytoplasmic granules are 

 under much closer nuclear control than the mitochondria and 

 the soluble proteins of the hyaloplasm. 



In summary, removal of the nucleus in the amoeba is 

 followed essentially by a drastic decrease of DPN, RNA, 

 acid phosphatase and esterase, g. marked fall in the incor- 

 poration of amino acids into proteins, a loss of the ability to 

 retain phosphorylated ATP under anaerobic conditions, and 

 a slow decrease of the total protein and dipeptidase content. 

 On the other hand, removal of the nucleus hardly changes 

 oxygen consumption, aerobic ATP, protease, amylase and 

 enolase. 



