Abstract

Ammonia assimilatory and ureide biogenic enzymes were measured in the cytosol fraction of pigeonpea nodules during the period 15–120 days after sowing. The activity of enzymes involved in the initial assimilation of ammonia, i.e. glutamine synthetase, glutamate synthase, asparagine synthetase and aspartate aminotransferase, substantially increased activities during the period of plant growth and reached a maximum value around 105 days after sowing. These increases paralleled the increase in nodule mass, nitrogenase activity and ureide content in nodules. Though no regular pattern was obtained for their specific activities, yet these activities when expressed relative to the specific activity of nitrogenase were many fold higher at each stage of development. Similar increases were observed in the activities of enzymes associated with the formation of ureides from purines. In almost all cases, the activities were again maximum around 90–105 days after sowing. The specific activities of nucleotidase, nucleosidase, xanthine dehydrogenase, uricase and allantoinase, when expressed relative to the specific activity of nitrogenase at vegetative, flowering and podsetting stages were again many fold higher indicating the sufficiency of the levels of these enzymes for the biosynthesis of ureides. The data presented are consistent with the proposal that in ureide producing legumes, ammonia is initially assimilated into glutamine, aspartate, etc., which are metabolised for the denovo synthesis of purines. The purines are then utilised for the production of ureides by a group of enzymes investigated here

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.