The Enzymic Incorporation of Iron into Protoporphyrin 



209 



Phillips (this Symposium, p. 32) showed that there was no chelation of iron 

 with protoporphyrin in the presence of a variety of Tweens. 



The activity of the extract is also heat-sensitive (Fig. 2). Treating the 

 extract at GO^C for 10 min destroys the activity almost completely. 



CO 

 Q 



< 

 in 



ZD 

 O 



X 



h- 





12 — 



8 



TWEEN ALONE 



HEATED 



EXTRACT 



2 4 



ml OF TWEEN EXTRACT 



Fig. 2. EfTect of detergent alone and heat on iron incorporation 



3 



en 



<r 2 



Z) 



o 



X 



h- 



CL 



jyVEEN EXTRACT WITH 

 MERCAPTOETHANOL 



TWEEN EXTRACT 

 I I 1 L_ ' 



J I I L 



-. 1 I I 



5 10 15 



DAYS 



Fig. 3. Duration of enzyme activity with Tween 40 and with mercaptoethanol. 



Increased stability of the enzyme solution is noted when Tween 40 is used 

 for its extraction from the centrifuged residue of the red cells. The duration 

 of enzyme activity in the original lysate is at most 24 hr, while in the Tween 

 extracts it is of the order of 10 days. If mercaptoethanol is added (final 

 concentration 00 1 m) the enzyme activity is increased and the duration of 



