ROLES OF UREASE IN PLANT-CELLS

This chapter discusses the role of urease in plant cells. Urease is important for efficient nitrogen assimilation. Considerable amounts of plant nitrogen flow through urea (urease substrate), which can be recycled only by urease action. This recapture can have significant quality impact on protein rich crops. It appears to have an important role in germination of protein poor seeds. The urease substrate urea is derived from arginine and ureides. Arginine is the richest nitrogen repository among the amino acids of seed storage proteins. On the other hand, ureides are not only significant sources of nitrogen in nucleic acid turnover but are also a predominant transport from of fixed nitrogen in soybean and other tropical legumes. Urease-negative plants accumulate substantial, nonutilizable urea in both maternal and embryonic tissue. During germination of urease-negative seeds, further urea accumulates as a dead end in nitrogen metabolism. Abundant seed ureases, such as, Sumner's jackbean urease, may play a chemical defense role. All of the ureases, both from bacteria and plants, resemble each other in primary structure and in their requirement for accessory genes. © 1993, Academic Press, Inc.