286 



H. CHANTRENNE 



was added to the bacterial extracts in certain experiments; this did not 

 change the resuhs appreciably. 



These results suggest that the protein moiety of catalase made during 

 the restoration period was abnormal, although the enzyme was active. 

 Considerable change in the protein moiety of catalase can probably be 

 brought about without changing much the catalytic properties of the haem; 

 to the contrary, the active centre of penicillinase must be a region of the 

 polypeptide, the catalytic properties of which are directly affected by 



Fig. 3. Changes in catalase properties. Extracts were prepared by sonication 

 from normal bacteria (•) and from bacteria which had been incubated with azagua- 

 nine for 45 min. before adding guanosine. These bacteria were collected i2omin. 

 after the addition of guanosine (O)- The catalase activity of the extracts was 

 determined according to von Euler and Josephson [21] at four different tem- 

 peratures: o", 15", 30 and 45". In the second experiment, an excess bovine serum 

 albumin was added to both extracts. The results are expressed as per cent of the 

 activity measured at o". 



malformations of the chain. This may account for the greater sensitivity 

 of penicillinase to the damages caused by azaguanine. 



Our results suggest that 8-azaguanine, like 2-thiouracil and 5- 

 fluorouracil, can affect the structure of the proteins produced by the 

 bacteria which have incorporated the analogue into their nucleic acids. On 

 the other hand, azaguanine exerts a general inhibition of protein synthesis, 

 most probably by disturbing the normal interactions between some soluble 

 and ribosomal ribonucleic acids. 



References 



Mandel, H. G.,J. biol. Chetn. 225, 137 (1957). 

 Chantrenne, H., Rec. Trav. chim. Pays-Bas 77, 586 (1958). 

 Chantrenne, H., and Devreux, S., Exp. Cell Res. Suppl. 6, 152 (1958). 

 Chantrenne, H., and Devreux, S., Nature, Lond. 181, 1737 (1958). 

 Chantrenne, H., and Devreux, S., Biochini. biuphys. Acta 39, 486 (i960). 



