Autoxidation of Flavocytochrome b.> 533 



exerted by lactate and the effect of metals place flavocytochrome b^ among 

 substances like cysteine and ascorbic acid, which are only autoxidizable in 

 the presence of metals. 



SUMMARY 



The oxidation of lactate to pyruvate, catalysed by flavocytochrome h^, was 

 studied using oxygen as the electron acceptor. The effects of the concentra- 

 tion of enzyme, lactate, oxygen, hydrogen ions, and of ionic strength were 

 studied. 



Under optimal conditions, 27 moles of oxygen were reduced/mole of 

 enzyme/min. One molecule of oxygen was consumed for each two molecules 

 of lactate dehydrogenated to pyruvate. 



Ferrous and ferric ions actively catalyse the autoxidation of flavocyto- 



Since preparation of this paper, crystalline flavocytochrome b^ has been obtained 

 according to the procedure described by Appleby and Morton (1954, 1959). 



A ckno wledgemen ts 



These investigations were supported by the Rockefeller Foundation and 

 the Comitato Nazionale per le Ricerche Nucleari. 



We thank Mr. Angelo Trussardi, Director of the Societa Anonima Distil- 

 lerie Italiane, Ferrara, for generous gifts of yeast. 



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

 Appleby, C. A. & Morton, R. K. (1959). Biochem. J. 71, 492. 

 Bach, S. J., Dlxon, M. & Zerfas, L. G. (1946). Biochem. J. 40, 229. 

 BoERi, E. & Tosi, L. (1956). Arch. Biochem. Biophys. 60, 463. 

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