Abstract
1. Cell-free extracts prepared from soya-bean nodule bacteroids produced HD from D2 in the presence of dithionite, an ATP-generating system and nitrogen. 2. Crude extracts of bacteroids or of Azotobacter vinelandii showed some background D2 exchange when any one of these was omitted. 3. Partial purification of bacteroid extracts diminished this background activity and gave increased D2 exchange and nitrogen fixation. 4. Although increasing pN2 stimulated both reactions, the apparent Km (N2) for nitrogen fixation was much higher than the apparent Km (N2) for D2 exchange when partially purified bacteroid extracts were used. 5. Carbon monoxide was a competitive inhibitor of nitrogen fixation by partially purified bacteroid extracts, but D2 exchange was inhibited in a non-competitive fashion. 6. These results are discussed in relation to the possible existence of enzyme-bound intermediates of nitrogen fixation.
Full text
PDFSelected References
These references are in PubMed. This may not be the complete list of references from this article.
- BERGERSEN F. J. The bacterial component of soybean root nodules; changes in respiratory activity, cell dry weight and nucleic acid content with increasing nodule age. J Gen Microbiol. 1958 Oct;19(2):312–323. doi: 10.1099/00221287-19-2-312. [DOI] [PubMed] [Google Scholar]
- DIXON M. The determination of enzyme inhibitor constants. Biochem J. 1953 Aug;55(1):170–171. doi: 10.1042/bj0550170. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HOCH G. E., SCHNEIDER K. C., BURRIS R. H. Hydrogen evolution and exchange, and conversion of N2O to N2 by soybean root nodules. Biochim Biophys Acta. 1960 Jan 15;37:273–279. doi: 10.1016/0006-3002(60)90234-1. [DOI] [PubMed] [Google Scholar]
- Jackson E. K., Parshall G. W., Hardy R. W. Hydrogen reactions of nitrogenase. Formation of the molecule HD by nitrogenase and by an inorganic model. J Biol Chem. 1968 Oct 10;243(19):4952–4958. [PubMed] [Google Scholar]
- Kelly M. Hydrogen-deuterium exchange reactions catalysed by nitrogenase. Biochem J. 1968 Sep;109(2):322–324. doi: 10.1042/bj1090322. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]