Il8 THOMAS P. SINGER 



12. Minakami, S., Ringler, R. L., and Singer, T. P., Biochem. biophys. Res. Comm. 

 3> 333 (i960). 



13. Estabrook, R. W., Fed. Proc. 16, 178 (1957). 



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15. Lusty, C. J., and Singer, T. P., to be published. 



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 O. H. Gaebler. Academic Press, New York, 447 (1956). 



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235. 535 (1960)- 



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19. Ringler, R. L.,_7. biol. Chem. 236, 1192 (1961). 



20. Warringa M. G. P. J., and Giuditta, A., J. biol. Cheyn. 230, iii (1958). 



21. Kearney, E. B.,_7. biol. Chem. 229, 363 (1957). 



22. Wosilait, W. D.,7- biol. Chem. 235, 1196 (i960). 



23. Ernster, L., Ljunggren, M., and Danielson, L., Biochem. biophys. Res. Comm. 

 2, 88 (i960). 



24. Marki, F., and Martius, C, Biochem. Z. 333, iii (i960). 



25. Mahler, H. R., and Elowe, D. G., J. biol. Cheyn. 210, 165 (1954). 



26. Vernon, L. P., Mahler, H. R., and Sarkar, N. F., J. biol. Chem. 199, 599 (1952). 



27. King, T. E., and Howard, R. L., Results presented at the 44th Annual Meet- 

 ing of the American Society of Biological Chemists, Chicago, April, i960. 



28. Personal Communication from Dr. T. E. King. 



Discussion 



Ernster : Does your enzyme react with quinones as electron acceptors ? 



Singer: We haven't had a chance to test it yet. 



Ernster : I should like to recall an interesting observation which Dr. Conover 

 and I made some time ago on a non-purified preparation of DPNH oxidase; we 

 found that with vitamin K3 as terminal electron acceptor we obtained an appreciable 

 amytal-sensitivity, whereas with i ,4-naphthoquinone the am^tal-sensitivity was only 

 marginal (cf. Ernster, this volume. Table 7, page 150). 



Note added in proof. The homogeneous enzyme contains about 16 atoms of non- 

 haem iron and i mole FAD per 10" g. protein. The pH optimum range, as deter- 

 mined by a transhydrogenase assay, is pH 8 to 9. In this range the turnover number 

 per mole of flavin is i • 3 million per minute at 30 . 



