210 



R. A. Neve 



activity extended an additional 4-5 days (Fig. 3). The stimulation by 

 mercaptoethanol is similar to that given by other sulphydryl compounds, 

 e.g. glutathione and cysteine, which are effective on both liver and red blood 

 cell extracts (Nishida and Labbe, 1959; Schwartz et al, 1959). 



In preliminary inhibition studies on the Tween extract, it was found that 

 lead acetate (10~^ m) in phosphate buffer inhibited the iron incorporation by 

 about 65%, while ethylenediaminetetraacetic acid (EDTA) (10~^m) was 

 completely inhibitory. 



On fractionation of the Tween extract with ammonium sulphate the major 

 part of the enzyme activity was found in the 50-60% saturated fraction 

 (Table 1). This is similar to the fractionation carried out by Minakami (1958) 



Table 1. Enzyme activity in the ammonium sulphate fraction 

 OF THE Tween-KHCO, extract 



who found the majority of the activity in the 50-75 % ammonium sulphate 

 fraction of a cholate extract of rat liver mitochondria. Refractionation of 

 the 50-60% fraction resulted in some increased purification (Table 1). 

 Further purification of this enzyme is in progress. 



Dresel, E 

 Grinstein 

 Heikel, T. 

 Krueger, 

 Labbe, R. 

 Labbe, R. 

 Minakami 

 Neilands, 

 p. 324. 



REFERENCES 



L B. & Falk, J. E. (1954). Biochem. J. 56, 156. 



M. (1947). J. biol. Chem. 167, 515. 



, LocKwooD, W. H. & Rimington, C. (1958). Nature, Land. 182, 313. 

 R. C, Melnick, L & Klein, J. R. (1956). Arch. Biochem. Biophys. 64, 302. 

 F. & Nishida, G. (1957). Biochim. biophys. Acta 26, 437. 

 F. (1959). Biochim. biophys. Acta 31, 589. 

 , S. (1958). J. Biochem. {Tokyo) 45, 833. 

 J. B. & Orlando, J. A. (1958). Int. Symp. Enzyme Chem. Maruzen, Tokyo, 



