Topographical Aspects of Metabolic Regulation 53 



but the exact relationship between these particles and 

 engulfing vacuoles remains to be established. 



The example just mentioned is a special one in that the 

 observed association could not be foreseen from previous 

 biochemical data and represents, in fact, the only reason for 

 considering the enzymes studied as linked together function- 

 ally. This is not the case for enzymes catalysing sequential 

 reactions and associated in one of the accepted metabolic 

 schemes of dynamic biochemistry. The existence of such 

 • schemes may, however, be misleading, since it is sometimes 

 forgotten that they rest not only on facts but also on our 

 interpretation of these facts and even on such chance factors 

 as have led to the elucidation of a given sequence of reactions 

 before another. In this respect, enzyme distribution studies 

 may provide information of paramount importance and help 

 us to distinguish between physiological and artificial poly- 

 enzymic systems. 



REFERENCES 



DE DuvE, C. (1957). Symp. Soc. exp. Biol., 10, 50. 



DE DuvE, C. (1959). In Subcellular Particles, in press. Washington: 



American Physiological Society. 

 DE DuvE, C, and Berthet, J. (1954). Int. Rev. CytoL, 3, 225. 

 Straus, W. (1956). J. hiophys. biochem. CytoL, 2, 513. 

 Straus, W. (1957). J. hiophys. biochem. CytoL, 3, 933, 1037. 



DISCUSSION 



Lehninger: Prof, de Duve, have you had occasion to repeat the 

 experiments of Dr. Straus (1957, loc. cit.) using your own method of 

 collection to see whether the peroxidase which Straus used is actually 

 liberated in the course of the lysis of the lysosomes? In his experiment 

 a small amount of crystalline peroxidase from horse radish was injected 

 intravenously into rats, and after a short time he isolated the lysosome 

 fraction and demonstrated the presence of the peroxidase which was 

 originally introduced intravenously in the droplets. This is a very 

 important piece of evidence for the pinocytosis theory. 



de Duve: No, we have not done so because Dr. Straus is shortly 

 joining us for some time, and we hope to be able to do this work with 

 him. 



Greville: To refer to the matter of opening up enzymes in the mito- 

 chondria, unmasking or rendering them less occult. Dr. J. B. Chappell 

 and I (1958, IV int. Congr. Biochem., Abstr. of Communications, p. 73) 



