SYNTHESIS OF RESPIRATORY ENZYMES 627 



temperature changes outside the body, or aging by storage, and partly 

 to immunologic factors. 



6. SYNTHESIS OF RESPIRATORY ENZYMES 



So far we know very little about the synthesis of the respiratory 

 enzymes. Since protoporphyrin or protohematin are required as 

 nutrients for the synthesis of respiratory enzymes and cytochromes 

 in certain microorganisms (cf. Section 3.2.2.), the former porphyrins 

 can be assumed to be intermediates in the synthesis of the enzymes. 

 Cytochrome c cannot replace protohematin. The hematin enzymes 

 of Hemophilus influenzae differ, however, from the usual cytochrome 

 oxidase system {1035).* Protoporphyrin is the only porphyrin into 

 which iron can be introduced by the organism; but mesohematin can 

 be used for the formation of the respiratory enzyme, although not 

 for that of a nitrate-reducing system for which protoporphyrin is 

 essential. 



Crandall and Drabkin {510a) found a rapid formation of cyto- 

 chrome c in regenerating rat liver tissue after partial hepatectomy, 

 but transport of the cytochrome from the skeletal muscle has not yet 

 been excluded. Benko {213a) found the cytochrome c content of 

 skeletal muscle, and to a smaller extent that of heart muscle, depressed 

 by factors inhibiting hemopoiesis, and Tissieres {2809a) found the 

 same after thyroidectomy or administration of thiouracil. 



Iron deficiency decreases the catalase content of mammalian 

 organs, except that of the heart (Schultze and Kuiken, 2^83). On 

 recovery the catalase is restored more rapidly than is hemoglobin. 

 No decrease of the cytochrome oxidase content of mammalian organs 

 in iron deficiency has been observed, but in bacteria cytochrome 

 oxidase is diminished, together with other hematin enzymes, such as 

 catalase and peroxidase, though to a smaller degree than the latter. 



Waring and Werkman {2960) found that the cytochrome absorp- 

 tion bands of Aerobacter indologenes disappear, if the organism is 

 made deficient in iron. They removed the iron with 8-hydroxy- 

 quinoline, a reagent which also removes copper, but could show by 

 readdition of iron that the observed effects were due to iron, not to 

 copper deficiency. The iron-deficient bacteria contained less catalase 

 (only 1 20), peroxidase, hydrogenase, cytochromes, and cytochrome 



* The hematin enzyme formed from porphyrin, iron, and toxin in Corynehacterium 

 diphtheriae is cytochrome b, according to Pappenheimer {210 !tb). 



