The Eiizymic Incorporation of Iron into Protoporphyrin 111 



c has been synthesized. In our in vitro studies (Marsh and Drabkin, 1957) it appears 

 safe to assume that biosynthesis (as distinguished from incorporation of isotope) had 

 actually occurred, since [2-"CJ glycine labels both the haemin and protein moieties, 

 and, indeed, there was an early separation in time of the two processes. The labelling 

 of the haemin cannot be ascribed to such reactions as transamidation, etc. This 

 apparently 'minor' issue is worthy of consideration in studies of protein biosynthesis 

 and deductions as to net synthesis. In vitro studies involve large losses due to leaching 

 of materials into the medium in the usual methods. Special respiration techniques 

 were developed (Drabkin and Marsh, 1956). 



(2) Cytochrome c behaves like an adaptive enzyme; it responds to functional need. 

 This is clear in the case of yeast grown anaerobically and then adapting to life in the 

 presence of oxygen (Yeas and Drabkin, 1957). But, the adaptive behaviour can be 

 deduced also from the increase in cellular cytochrome c in the experimentally induced 

 hyperthyroid state (Drabkin, 1950a, 1951a, 1955). 



(3) Cytochrome c is important in the growth of tissues and in protein synthesis. 

 This role of cytochrome c is related to its adaptive behaviour. The concentration of 

 cytochrome c increases in liver regenerating after partial hepatectomy (Crandall and 

 Drabkin, 1946). Moreover, the full restoration of cytochrome c as well as RNA in 

 regenerating rat liver precedes appreciable tissue regrowth (Drabkin, 1947a and b). 

 It has been proposed accordingly that protein synthesis is 'triggered' by cytochrome c 

 and ribonucleic acid. The mitochondrial particle fraction, which contains the cyto- 

 chrome c is increased in volume during liver restoration (Drabkin, 1950b). 



In our more recent work we have been concerned with the elaboration of details 

 in the biosynthesis of cytochrome c and haemoglobin, as well as with the development 

 of suitable techniques for the efficient recovery of cytochrome c from rat liver 

 mitochondria. 



These investigations were supported by grants from the Office of Naval Research 

 and the Bureau of Medicine and Surgery of the Navy (U.S.). 



REFERENCES 



Crandall, M. W. & Drabkin, D. L. (1946). /. biol. Cliem. 166, 653. 



Drabkin, D. L. (1947a). J. biol. Client. Ill, 395. 



Drabkin, D. L. (1947b). /. biol. Chem. 171, 409. 



Drabkin, D. L. (1950a). /. biol. Chem. 182, 335, 



Drabkin, D. L. (1950b). J. nat. Cancer Inst. 10, 1357, 1360. 



Drabkin, D. L. (1951a). Physiol. Rev. 31, 345. 



Drabkin, D. L. (1951b). Proc. Soc. exp. Biol. Med. 76, 527. 



Drabkin, D. L. (1955). Porphyrin biosynthesis and metabolism, Ciba Foundation 



Symposium (Ed. by G. E. W, Wolstenholme and E. C. P. Millar), p. 96, London. 

 Drabkin, D. L. & Marsh, J. B. (1956). /. biol. Chem. 11\, 71. 

 Marsh, J. B. & Drabkin, D. L. (1957). J. biol. Chem. IIA, 909. 

 Theorell, H., Beznak, M., Bonnichsen, R., Paul, K. G. & Akesson, A. (1951). 



Acta chem. Scand. 5, 445. 

 YcAS, M. & Drabkin, D. L. (1957). J. biol. Chem. 224, 921. 



Morton : It may be of interest to recall that, since the in vitro biosynthesis of cytochrome c 

 was so elegantly opened up by Drabkin, Simpson and co-workers have shown net 

 biosynthesis of cytochrome c in calf-heart mitochondria (Bates, Kalf and Simpson : 

 Fed. Proc. 18, 187, 1959). 



