Molybdenum and Nitrate Reductase

Numerous investigators have shown that nitrate nitrogen accumulates in higher plants (l-3) and fungi (2, 4) which are deficient in molybdenum. Other workers have shown that sulfur, zinc, and manganese deficiencies in higher plants may also result in a similar phenomenon (5). The free amino acids present in molybdenum-deficient plants are usually less than those in normal tissues, thus indicating that molybdenum is important for the metabolism of nitrogen (2.-4). The function of molybdenum in enzyme systems involved in the utilization of nitrogen has not hitherto been established. The characterization of nitrate reductase, including evidence for the presence of a metal component, and the demonstration that iron, manganese, and zinc deficiencies actually increased the specific activity of the enzyme (6) prompted an investigation of the effect of molybdenum deficiency on nitrate reductase. This paper elaborates a preliminary report (7) in which it was shown that molybdenum is specifically required in the nutrient medium for the activity of nitrate reductase in the fungi Neurospora crassa and Aspergillus niger.