522 R. K. Morton, J. McD. Armstrong and C. A. Appleby 



A similar rate equation is obtained for mechanism // (a) (cf. p. 516). The 

 corresponding rate equations for one-electron acceptors have the same 

 general form, but require certain restrictions as to rate-limiting steps for their 

 derivation. 



III. (cf. p. 517) E-fS ^^ES (1) 



k, 



ES-E'-fP (10) 



E'-i-A^E + H^A (11) 



k. + k^ 



k,m y ^ k,[E] ^^^^ ^ ^ A-i 



A'3 A'2 -j- A'3 A'3 "^ A'a 



^ MA] + A'JS] + /^ L "^ 'km. 



For a one-electron acceptor: 



E -f S 4 ES (I) 



ES-^E"-1-P (12) 



E"4- A^E'-f-HA (13) 



E'-fA^E-hHA (14) 

 A-.3[E] 



klk^ + A-^) k^ + A-3 

 k,k,{K\ ^ AJS] 



As indicated above, some consideration has been given to the cases for 

 one-electron and two-electron acceptors, and it has been found that the types 

 of mechanisms given hold for either case, provided some minor modifications 

 of the detailed mechanisms are made. In the early part of the reaction, the 

 flavin moiety is probably alternately oxidized and reduced between the fully 

 reduced and 5'e/«/quinone states, without ever reaching the fully oxidized 

 slate. This assumption results in some simphfication of the postulated 

 mechanisms. 



Acknowledgement 



One of us (J. McD. Armstrong) is grateful to the Commonwealth Scientific 

 and Industrial Research Organization for a Senior Studentship. 



REFERENCES 



Alberty, R. a. (1956). Advanc. Enzymol. 17, 1. 



Appleby, C. A. (1957). Ph.D. Thesis, University of Melbourne. 



Appleby, C. A. & Morton, R. K. (1954). Nature, Loml. 173, 749. 



