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Biomedical subjects

J Rigaud

Publications and source records attributed to J Rigaud.

53 records · Page 3Linked to original sources
PubMed1977

Effect of nitrite upon leghemoglobin and interaction with nitrogen fixation.

Nitrite (0.4 mM) added to soybean bacteroid preparations strongly inhibited C2H2 reduction. In the presence of leghemoglobin (0.1mM), a 3-fold enhancement of nitrogen fixation occurred but the inhibitory effect of nitrite was delayed. Spectra of leghemoglobin showed a rapid disappearance of the 574 nm and 541 nm peaks of oxyleghemoglobin the presence of nitrite. Concomitant oxidation of this hemoprotein gave ferric leghemoglobin as the single final product. High nitrite levels could depress nitrogen fixation both by inactivation of nitrogenase and by conversion of leghemoglobin into an inactive form. Nitrite present at low concentrations reacts with this hemoprotein and is then no longer able to penetrate into bacteroids.

Hemeproteins↗
PubMed1975

Nitrate reductase from bacteroides of Rhizobium japonicum: enzyme characteristics and possible interaction with nitrogen fixation.

The soluble nitrate reductase of Rhizobium japonicum bacteroids has been purified and its properties compared to those of aerobically grown cells. The enzymes from both sources are similar with molecular weights of about 70 000 suggesting no close relationship with the molybdo-protein component of nitrogenase. Nitrite, the product of nitrate reductase, strongly inhibited the nitrogenase activity from bacteroids, at concentrations less than 100 muM. Thus, an interference in the rate of nitrogen fixation is possible as a result of nitrate reductase activity. A study of the distribution of nitrate reductase in bacteroids indicates that a proportion of the total activity is membrane-bound but that this activity is similar to that in the soluble fraction. Purified nitrate reductase required reduced viologen dyes for activity. Neither NADPH or NADH or FAD could substitute as electron donors. Dithionite is a strong inhibitor and inactivated nitrate reductase from all sources examined. This inactivation is prevented by methyl viologen. Purified nitrate reductase from bacteroids and bacteria Rhizobium japonicum is practically unaffected by exposure to oxygen.

Chromatography, Gel↗