Lysosome-vacuolar apparatus acid hydrolase control

The above brief comments on the model of the lysosome-vacuolar apparatus help define the horizons for subsequent discussion. This discussion is centered on the problem of control of hydrolytic activity by the lysosome-vacuolar system. Examination of the model brings into focus the major elements which may be involved in controlling intracellular degra-dative activity, itself poised upon the normal functioning of the lysosome-vacuolar system. We may state here that control of acid hydrolase... 

The catabolic activities of the acid hydrolases occur either extracellu-larly through the process of exocytosis or intracellularly. Here we shall consider control of the catabolic hydrolysis occurring through activity of intravacuolar add hydrolases. Figure 1 diagrams the membrane system associated with the lysosomal-vacuolar apparatus and its catabolic activity and portrays the central role of the membrane-sequestered digestive vacuole. Biochemical studies of the lysosome-vacuolar system have al-... 

Any detailed discussion of these individual phases must be speculative, but is valuable because of the critical importance of membrane fusion in the control of acid hydrolase activity in the lysosome-vacuolar apparatus. 

Acid hydrolase activity is poised for optimal activity and control by the nature of the enzyme microenvironment within the lysosome-vacuolar apparatus. A significant feature of this control has already been discussed in Section VI A.l. It was demonstrated that an interposed membrane precluded normal access of substrate to active site. In this section we will consider those factors which allow for optimal hydrolase activity within the compartmentalized vacuolar system. It must be realized that the lysosome-vacuolar system is maintained in a dynamic state and that trans-membrane diffusion of intermediates and metabolites may be oc-... 

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