STRUCTURAL AND CHEMICAL ARCHITECTURE OF HOST CELLS 81 



D. Enzymatic Systems of Cytoplasm 



1. Mitochondria 



Tables VII and IX reveal the large number of enzymes present in the 

 mitochondria of rat liver, as well as the relatively high concentration of many 

 of these and a number of vitamins, coenzymes, and metabohtes 



A number of these enzymes, e.g., acid phosphatase, ATPase, glutamic 

 dehydrogenase, etc., are "latent" or inactive when the mitochondria are 

 isolated in an undamaged state. Disruption of the membrane permits 

 demonstration of these enzymatic activities. Further disruption by mechan- 

 ical means reveals two major classes of mitochondrial enzymes, an insoluble 

 phosphorylating carrier of respiratory systems and ATPase, and a number 

 of soluble enzymes which include glutamic dehydrogenase, adenylate kinase, 

 fumarase, etc. Treatment of the insoluble fragments with sodium cholate 

 destroys the phosphorylatmg abiUty without affecting respiratory activity 

 (Gamble and Lehninger, 1956). 



A soluble heme protein, termed mitochrome, which inhibits the aerobic 

 phosphorylation of fresh mitochondria, has recently been isolated after 

 release by aged or otherwise degraded mitochondria (Polis and Shmukler, 

 1957). Mitochrome appears to be involved in the action of the hidden ATPase 

 of intact mitochondria, and it has been suggested that these structures are 

 integrated in some way to effect a binding of inorganic phosphate and transfer 

 of this moiety to ATP during oxidative phosphorylation. 



From these tables it is clear that in animals mitochondria are the major 

 cell centers of respiration, i.e., of hydrogen and electron transport terminating 

 in reaction with molecular Og, since this particle contains all the c3d;ochrome 

 oxidase of the cell (Hogeboom et al., 1946; Martin and Morton, 1956). At 

 particular stages in the life cycle of some plants, polyphenol oxidase and 

 ascorbic acid oxidase may make the most quantitatively significant con- 

 tributions to O2 consumption (James, 1953). Although in plants both cyto- 

 chrome oxidase and poljrphenol oxidase are associated with mitochondria, 

 ascorbic acid oxidase is reported to be associated with the cell surfaces 

 (Goddard and Stafford, 1954). In bacteria, the work of WeibuE (1953a,b) 

 showed that the cytochromes of B. megatherium existed on the membrane of 

 the protoplast, i.e., the cytoplasmic membrane (Murray, 1957) remaining 

 after the cell wall of the bacterium was stripped off by lysozyme m the 

 presence of hypertonic sucrose. In addition, bacteria react with Janus green 

 at the cell periphery, leading to the suggestion that in bacteria these oxidative 

 sites exist in particles, which may form a continuous layer immediately 

 within the ceU wall (Alexander, 1956). Many workers have described the 

 isolation of cytochrome-containing particles from bacteria; however, these 

 particles are now thought to result from the disruption of the fragile 

 protoplast membrane. 



