425 Thiophenes, Imidazoles, Thiazoles, Isoxazoles 



The mode of action of biotin is known now in enough 

 detail to suggest the scheme outUned below. It is still un- 

 certain which nitrogen atom of the biotin molecule par- 

 ticipates.-"^ 



O 



II 



/\ 

 HN NH 



I I ATP 



HC CH > 



HoC CH—(CH..)4— COO— Enzyme 



o 



II 



o o 



T r 



Adenosine— O—P—O—P N NH 



OH OH HC CH 



CH2 CH—(CH2)4— COO— Enzyme 



or 

 O O 



T T 



Adenosine — O — P — O — P O 



OH OH 



i 



O o 



II II 



©O N NH 



R I I 



R— COOH < HC CH 



HN N 



I I 



HC CH 



I I 



CH2 CH—{CH2)4— COO— Enzyme 



I CO2 



H2C CH—{CH2)4— COO— Enzyme 



^^Salih J. Wakil, Edward B. Titchener and David M. Gibson, 

 Biochim. et Biophys. Acta 29 225 (1958); Salih J. Wakil, /. Am. 

 Chem. Soc. 80 6465 (1958). 



