13^ 



SUBCELLULAR PARTICLES 



the microsomal glucose-6-phosphatase. Subsequent investigations, performed in- 

 dependently by Novikoff, Podber, Ryan and Noe (67, 68), and in this laboratory 

 (22, 27, 3), showed that the dissociation between bound acid phosphatase and 

 cytochrome oxidase or succinoxidase could be magnified by centrituging and 

 washing under suitably chosen conditions. While the former authors interpreted 

 their results in terms of the heterogeneity of the particles, our experiments led 

 us to the conclusion that acid phosphatase is probably attached to a special group 

 of particles entirely distinct from the oxidizing mitochondria. This interpreta- 

 tion has also been favored by Kufi, Hogeboom and Dalton(58), by Thomson 

 and Moss (99), and by Thomson and Klipfel (97), who have confirmed the above 

 results by means of density-gradient centrifugation, and it has now been adopted 

 by NovikofJ(65). 



As a result of the investigations on acid phosphatase, a modified fractionation 

 scheme with greater discriminating power (fig. 2B) was worked out (3). In 

 experiments performed according to this scheme, cathepsin, acid ribonuclease, 

 acid deoxyribonuclease (DNA-ase II) and a large part of /^^-glucuronidase were 



A. CLASSICAL SCHEME 



B. NEW SCHEME 



CYTOCHROME 

 OXIDASE 



ACID 



PHOSPHATASE 



GLUCOSE - 6 - 



PHOSPHATASE 





20 



40 



so 



20 



40 



so 



20 



40 



60 



SO 



so 



80 



100 



20 40 60 so 100 



100 



100 



20 



40 



60 



SO 



100 



Fig. 2. Results of fractionation experiments, expressed as in de Duve et iil. (29). Ordinate: 

 relative specific activity = activity per mg N of fraction/activity per mg N of homogenate. 

 Abscissa: percentage of total N in fraction. Filled-in areas represent free activities. A, conven- 

 tional fractionation scheme; order of jnictions: nuclei, mitochondria, microsomes, supernatant. 

 B, .scheme of de Duve et ul. (29); order of fractions: nuclei, heavy and light mitochondria, 

 microsomes, supernatant. 



