Properties of Cytochrome bg 



517 



K^n + 



1 + 



K. 



Ka^ 



K, 



y.= 



[A] [A][S] [S] 



1 + 



[A] 



and K,„ = 



[A] 



1 + 



Ka 



[A] 



These mechanisms cannot be distinguished between by steady state kinetics. 

 V^ and K„,^ are the values obtained from Lineweaver-Burk plots at any 

 acceptor concentration [A]^,, and approach limit values of V and K^ as [A]„ 

 approaches infinity. The slope of the Lineweaver-Burk plots, K,„JV^ depends 

 on [A]j.. It will be noted that V^ is a hyperbolic function of [AJ^., while K^^ 

 contains terms which are hyperbolic and inverse functions of [A]^. 



III. Formation of an intermediate reduced form of enzyme (see Alberty, 

 1956). 



E + S ^ ES 



ES ^ E + P 



E + Aox -^ E + Ared 



'/[A], 



Fig. 4. Types of plots obtained for various mechanisms of flavin-linked dehydro- 

 genases (see text). 



Plots A and B. Plots of \\v against 1/[S] for varying acceptor concentrations [A]. 

 Curves (oi, a^ and a^ are shown for conditions [A]i < [AJa < [AJs. 

 Plot A is for mechanisms / and //. 

 Plot B is for mechanism ///. 



Plots C and D. Plots of \\K,,,^ or \\V^ against 1/[AL, where [AL is any acceptor 

 concentration. 

 Plot C is for mechanism /. 

 Plot D is for mechanism ///. 



