Pfizer Handbook of Microbial Metabolites 426 



It is probable that biotin is attached to the enzyme in an 

 amide linkage, perhaps at the t-amino group of a lysine 

 unit. Evidence indicates that a variety of apoenzymes 

 can use biotin as the prosthetic group in reversible carbon 

 dioxide transfer just as a variety of apoenzymes can use 

 riboflavin in reversible hydrogen transfer. 



Biocytin is a biotin-lysine conjugate isolated from con- 

 trolled autolysates of yeast cells. ^^' ^^ 



HN NH 



1 1 



HC CH O 



1 I II 



H2C CH— (CH2)4— C— NH— (CH2)4— CH— COOH 



NH2 



Biocytin 



O 



II 



.Cx 



o 



\ 



HN NH C NH 



CH CH CH2 CH— (CH2)5— COOH 



1 I \c/ 



CH3 CH2— (CH2)4— COOH ^ 



Dethiobiotin Actithiazic Acid 



It is better utilized by some microorganisms than is biotin 

 itself. 



Actithiazic acid is a biotin antimetabolite. 



The biosynthetic origin of biotin remains obscure. Pi- 

 melic acid is an effective precursor in biotin-producing 

 organisms. Dethiobiotin is produced by a Penicillium 

 chrysogehum mutant, and it may be an intermediate in 

 the biosynthetic scheme at least in this and probably in 

 other microorganisms.^^ 



^^ Lemuel D. Wright, Emlen L. Cresson, Helen R. Skeggs, Thomas 

 R. Wood, Robert L. Peck, Donald E. Wolf and Karl Folkers, ibid. 74 

 1996 (1952). 



■^- Donald E. Wolf, John Valiant, Robert L. Peck and Karl Folkers, 

 ibid. 74 2002 (1952). 



3'' E. L. Tatum, /. Biol. Chem. 160 455 (1945). 



