Cell compartmentation

A. Wiemken, in Cell Compartmentation and Metabolic Channeling (L. Nover, F. Lynen, and... 

Lindsay M. R., Webb R. L, Strous M., Jetten M. S. M., Butler M. K., Forde R. J., and Fuerst J. A. (2001) Cell compartmentalization in planctomycetes novel types of structural organization for the bacterial cell. Arch. Microbiol. 175, 413-429. 

Sine, P. (1980). General principles of cellular compartmentation. In Cell Compartmentation and Metabolic Channelling (Nover, L., Lynen, F., Mothes, K eds.), pp. 17-32, Elsevier/North-Holland, New York. 

Gopalakrishna R, Chen Z-H, Gundimeda U. 1997a. Selenocompounds induce a redox modulation of protein kinase C in the cell, compartmentally independent from cytosolic glutathione Its role in inhibition of tumor promotion. Arch Biochem Biophys 348(l) 37-48. 

Fig. 138. Three different interpretations of the adult Purkinje cell compartmentalization for Zebrin in the cerebellum of adult Monodelphis, illustrated in Fig. 136, are possible. A. The P2+ (dark grey) and P3 + (medium grey) bands are continuous and unbranched from lobule I to X. B. P2+ is continuous and unbranched, but a novel Zebrin 11+ band is inserted between PI and P2 in lobules VI to X (unshaded). C. P2+ bifurcates within lobule V to give two branches in lobules VI. Dore et al. (1990).

In the cell, compartmentation of enzymes into multienzyme complexes or organelles provides a means of regulation, either because the compartment provides unique conditions or because it limits or channels access of the enzymes to substrates. Enzymes or pathways with a common function are often assembled into organelles. For example, enzymes of the TCA cycle are all located within the mitochondrion. The enzymes catalyze sequential reactions, and the product of one reaction is the substrate for the next reaction. The concentration of the pathway intermediates remains much higher within the mitochondrion than in the surrounding cellular cytoplasm. 

Some cells don t have the option to rebuild a new protein every half hour and get on with it. These cells compartmentalize, putting the dangerous oxygen-using enzymes behind a protective barrier. The size, flexibility, and strength given by cholesterol helped build such barriers. 

Attempts to unravel the problems posed by cell compartmentation are hampered by the extreme difficulty of determining the exact intracellular location of many enzymes, let alone the distribution of metabolites. Even within a compartment distribution may not be uniform. For example, the existence of multienzyme systems, in which each enzyme is adjacent to the next one in the metabolic pathway, limits the diffusion of metabolites from the site of their production. This inequality of distribution of metabolites within the cell makes it difficult to demonstrate in vitro control processes which may occur in vivo. 

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