138 



SUBCELLULAR PARTICLES 



lOO 



PERCENTAGE OF 



MAXIMUM ACTIVITY 



SO 



60 



40 



20 



SUCROSE CONCENTRATION , M 



0.05 



0.10 



0.15 



0.20 



0.25 



Fig. 7. Osmotic activation of mitochondrial and lysosomal enzymes. Washed mitochondrial 

 fraction exposed for 15 min. to sucrose concentrations indicated in abscissa and then brought 

 back in 0.25 m sucrose. Free acid phosphatase activities measured as in Gianetto and de Duve 

 (38). Free dehydrogenase activity determined spectrojihutometrically at 550 m^ in the presence 

 of DPN, purified DPN-cytochrome c reductase antl cytochrome r, according to original tech- 

 nique of Bendall (9). 



fore, one is dealing with a single population of particles, within which variations 

 in enzymic content, correlated with size and density hut not with sensitivity to 

 rupturing agents, may occur; or there are two or more populations, up to one per 

 enzyme, differing slightly in size and density, but not in sensitivity to rupturing 

 agents. The biochemical evidence at present available does not enable us to dis- 

 tinguish between these possibilities. Neither do the physiopathological data. As 

 will be shown below, these indicate that the levels of lysosomal enzymes in the 

 liver are not controlled in bulk and may suffer considerable independent varia- 

 tions, but that their release occurs simultaneously in vivo as it does in vitro. 



Particularly delicate in connection with these problems is the case of uricase. 

 Novikoff et al. (67, 68) were the first to point out the similarity in distribution 

 between this enzyme and acid phosphatase. Their results have been confirmed by 

 a number of authors (98, 59, 29, 58, 99, 97), and it is generally assumed that the 

 two enzymes belong to the same particles (47). However, uricase is fully active 



