BIOTIN 



557 



analogues, the organism must be specified. While biotin sulfone can, in 

 the presence of aspartic acid, replace biotin in stimulating the growth of 



CO 



HN 

 Hi- 



h 2 c 



NH 



CH— (CH 2 ) 4 — COOH 

 "SC-2 

 biotin sulfone 



CO 

 HN NH 



HC CH 



H 2 C CH— (CH 2 ) 5 — COOH 



V 



homobiotin 



Saccharomyces cerevisiae, it is an effective antagonist of biotin for 

 Lactobacillus casei. Even homobiotin is not a particularly effective an- 

 tagonist of biotin for Lactobacillus arabinosus. 



Analogues of Oxybiotin (O-Heterobiotin). The activities of the hom- 

 ologues of oxybiotin and related compounds are indicated in Table 16. 

 Oxybiotin analogues are either inactive or relatively ineffective in pre- 

 venting the functioning of biotin, but they may prevent the utilization 

 of oxybiotin. It appears that oxybiotin and its analogues do not combine 



as strongly with the enzyme involved as does biotin and its corresponding- 

 analogues. The preparation of the lower and higher homologues of oxy- 

 biotin has allowed some comparison of their inhibitory activities in the 

 presence of oxybiotin with the activities of the corresponding analogues 

 of biotin in the presence of biotin. For Saccharomyces cerevisiae, dl- 



