1. Formerly a general term used to describe enzyme systems that catalyze the reduction of molecular nitrogen to ammonia in nitrogen-fixing bacteria; now specifically applied to enzymes that carry out this reaction with reduced ferredoxin and ATP; typically nitrogenase consists of two components, the first of which reduces N2 whereas the second transfers electrons.
The definition information for nitrogenase is provided by Stedman's. You can search our medical dictionary here.
Stedman's, part of Lippincott Williams & Wilkins, provides a comprehensive line of health-science publications for healthcare professionals and medical students.