LYSOSOMES, A NEW GROUP OF CYTOPLASMIC PARTICLES I45 



philic corpuscules of alveolar epithelium and Kupffer cells (H7), the lipid bodies 

 of pigeon breast muscle (53), the globoid bodies of HeLa cells (43) and the iron 

 particles of erythroblasts and erythrocytes ( 15). However, since the common 

 structural characters of lysosomes — if they have any — are not yet known, the sig- 

 nificance of these observations cannot be assessed at the present time. 



Lower Organisms. In a series of investigations on the giant amoeba Chaos 

 chaos, Holter (49, 50) has fountl lliat acid phosphatase and cathepsin, like suc- 

 cinic dehydrogenase, accumulate in the centrifugal pole when the intact cell is 

 centrifuged, but, unlike the latter enzyme, become unsedimentable in homo- 

 genates. He concludes that the hydrolytic enzymes may be attached to a special 

 group of particles analogous to the hepatic lysosomes. 



Conclusion. The fragmentary results obtained so far make it clear that lyso- 

 some-like particles are not confined to liver. They certainly occur in kidney, possi- 

 bly also in brain, spleen and other tissues, as well as in some lower organisms. 

 In addition, it must be remembered that lysosomal enzymes are widely distributed 

 and that their appearance in free form in some homogenates does not necessarily 

 disprove the existence of lysosomes in the intact cell, since the particles may be 

 disrupted by the homogenizing process, as appears to be the case with amoeba. 

 It is however much too early to decide whether lysosomes represent a cell organelle 

 of general significance or are restricted to some kinds of cells only. 



PHVSIOPATHOLOGICAL ROLE OF LYSOSOMES 



General Considerations. Obviously, the possible biochemical functions of the 

 lysosomes are circumscribed by the activities of their enzymes. These include 

 at least six and probably more soluble acid hydrolases capable of acting on the 

 most important cell constituents (see fig. i), a fact which is rendered all the more 

 significant by the absence of numerous metabolically active enzymes and of sev- 

 eral neutral and alkaline hydrolases. The next step in our reasoning is a little 

 more delicate, since the identified hydrolases can catalyze synthetic processes and 

 transfer reactions, as well as hydrolytic splittings. In our opinion, an essentially 

 hydrolytic function of the lysosomal enzymes is supported by the following 

 arguments: 



/) Very special conditions are needed for the spontaneous reversal of a hydro- 

 lytic reaction, especially in an aqueous medium. That such conditions could be 

 realized simultaneously for numerous compounds appears improbable and most 

 recent developments concur in showing that the cell does not rely on such re- 

 versals for its syntheses, but makes use of special activating mechanisms. This is 

 now known to be true for most of the substrates which are split by the lysosomal 

 enzymes. 



2) Transfer reactions, although not subjected to such thermodynamic barriers, 

 do in fact require conditions very similar to those which tavor the synthetic 



