Effect of nitrite upon leghemoglobin and interaction with nitrogen fixation

Area of Science:

• Biochemistry
• Plant Science
• Microbiology

Background:

• Nitrogen fixation is crucial for plant growth.
• Soybean bacteroids are key nitrogen-fixing symbionts.
• Leghemoglobin's role in nitrogen fixation is vital.

Purpose of the Study:

• To investigate the impact of nitrite on soybean nitrogen fixation.
• To understand the interaction between nitrite, leghemoglobin, and nitrogenase.

Main Methods:

• Soybean bacteroid preparations were used.
• Acetylene reduction assay measured nitrogenase activity.
• Spectrophotometry analyzed leghemoglobin changes.

Main Results:

• Nitrite strongly inhibited acetylene reduction.
• Leghemoglobin (0.1mM) enhanced nitrogen fixation but its inactivation by nitrite was delayed.
• Nitrite oxidized oxyleghemoglobin to inactive ferric leghemoglobin.
• High nitrite levels inactivated nitrogenase and leghemoglobin.

Conclusions:

• Nitrite inhibits nitrogen fixation by inactivating nitrogenase.
• Nitrite converts leghemoglobin to an inactive form.
• Low nitrite concentrations react with leghemoglobin, preventing bacteroid penetration.