Lysosomes, a Neiv Group of Cytoplasmic Particles 



C. deDUVE 



University of Louvain 

 Louvain, Belgium 



THE CONCEPT THAT THE HEPATIC CELL Contains a special group of lytic par- 

 ticles has emerged from studies on the unspecific acid phosphatase of rat 

 liver, which were later extended with similar results to a number of other hydro- 

 lases. The subsequent recognition that droplets isolated from kidney tissue are 

 analogous to the hepatic lysosomes, together with recent observations indicating 

 the presence of similar particles in several other tissues as well as in some lower 

 organisms, has opened the possibility that lysosoines may represent organelles of 

 fairly wide significance. Speculations as to their physiological function have been 

 stimulated by various morphological and biochemical studies suggesting a possible 

 involvement of lysosomes in intracellular digestion, in connection with phenom- 

 ena of phagocytosis, athrocytosis and pinocytosis. Other experiments indicate 

 that they may play a significant role in autolysis and necrosis. 



Although adequate documentation is still lacking on many of these points, 

 enough data have already been gathered to warrant a survey covering the present 

 status of the problem. In particular, a precise definition of the lysosome concept, 

 together with a critical discussion of its experimental basis, has been deemed 

 necessary in view of the loose manner in which these particles are sometimes re- 

 ferred to, considered as mitochondria, or confounded with the fractions in which 

 they are concentrated. 



LIVER LYSOSOMES 



Definition and Main Properties. The name 'lysosomes' designates a special 

 class of particles present in suitably prepared rat liver homogenates (29). The 

 term has this peculiarity, that it refers to what is believed to be a morpho- 

 logically distinct entity, defined on the basis of purely biochemical data. As will 

 be shown below, a tentative morphological identification of lysosomes has been 

 made, but definite proof of its correctness is still lacking and it seems preferable 

 to retain the name in its original connotation, at least provisionally. 



The simplest (though not the only possible one; see the discussion in indi- 

 viduality AND homogeneity) Schematic representation of lysosomes, embodying 

 most of the biochemical evidence available at the present time, is shown in fig- 

 ure I. The diagram, which is largely self-explanatory, stresses the following 

 properties of the particles: /) dimensions corresponding, in 0.25 m sucrose and 



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