224 E- ^' SLATER, M. J. BAILIE AND J. BOUMAN 



Conclusion 



Our results agree with those of Klingenberg and Slenczka [8] in that 

 they fail to show the presence in most preparations of fresh rat-liver 

 mitochondria of detectable amounts of the "extra DPN " of Purvis. We 

 do, however, often find appreciable amounts of a compound with the 

 properties of "extra DPN" after incubation of the mitochondria with 

 substrate, in the absence of Pj. Rabbit-heart and pigeon-breast sarcosomes 

 are a much more consistent source of "extra DPN". 



Further work is required to establish the significance of the "extra 

 DPN" and it would be premature to speculate on its nature. Concerning 

 whether it is more likely to be a DPN + or a DPNH compound, the reader 

 is referred to a discussion between one of the writers and Dr. B. Chance, 

 published in the Proceedings of the International Symposium on Haem 

 Compounds (Canberra, 1959). 



Acknowledgments 



These studies have been supported in part by a grant from the Life 

 Insurance Medical Research Fund. One of us (M. J. B.) is a recipient of 

 personal grants from the Netherlands Ministry of Education and the Anti- 

 Cancer Council of Victoria, Australia. We wish to thank Dr. J. P. Colpa- 

 Boonstra and Mr. A. Perk for their collaboration in some of these experi- 

 ments. Dr. J. L. Purvis for making available Fig. i, and Mr. B. Winter, 

 Miss M. A. Searle, and Mr. J. G. Huisman for their technical assistance. 



References 



1. Taylor, J. F., Velick, S. F., Cori, G. T., Cori, C. F., and Slein, M. W., J. 

 biol. Chem. 173, 6iq (1948). 



2. Huennekens, F. M., and Green, D. E., Arch. BiocJiem. Biop/iys. 27,418 (1950). 



3. Lehninger, A. L,.,y. biol. Cliem. 190, 345 (1951). 



4. Christie, G. S., and Judah, J. D., Proc. roy. Soc. B 141, 420 (1953). 



5. Kaufman, B. T., and Kaplan, N. O., Biochim. biophys. Acta 39, 332 (1960). 



6. Birt, L. M., and Bartley, W., Biochem.J. 75, 303 (i960). 



7. Chance, B., and Williams, G. ^.,J. biol. Chem. 217, 409 (1955). 



8. Klingenberg, M., and Slenczka, W., Biochetn. Z. 331, 486 (1959). 



9. Klingenberg, M., Slenczka, W., and Ritt, E., Biochetn. Z. 332, 47 (1959). 



10. Purvis, J. L., Nature, Loud. 182, 711 (1958). 



11. Purvis, J. L., Biochim. biophys. Acta 38, 435 (i960). 



12. Helton, F. A., Biochem.J. 61, 46 (1955). 



13. Glock, G. E., and McLean, P., E.xp. Cell Res. 11, 234 (1956). 



14. Jacobson, K. B., and Kaplan, N. 0.,jf. biol. Chem. 226, 603 (1957). 



15. Holton, F. A., Hulsmann, W. C, Myers, D. K., and Slater, E. C, Biochem.J. 



67> 579 (1957)- 



16. Chance, B., and Williams, G. R., J. biol. Chem. 217, 395 (1955). 



