Abstract
The influences of different nitrogen sources on the relative rates of biosynthesis of glutamine and alanine have been studied by 15N nuclear magnetic resonance spectroscopy of intact Neurospora crassa mycelia suspensions. The rate of glutamine synthesis was fastest after growth in media deficient in free ammonium ion, whereas it was slowest following growth in media containing both glutamic acid and glutamine. The reverse trend was observed for the biosynthesis of alanine. A competition between the two biosynthetic pathways for the same substrate, glutamic acid, was found to limit the rate of alanine synthesis when glutamine synthesis was rapid. The observed in vivo rates of these reactions are compared to the reported specific activities of the enzymes catalyzing the reactions, and implications of these results for nitrogen regulation of these pathways under various physiological conditions are discussed.
Highlights
From the 8Gatesand Crellin Laboratories of Chemistry, California Institute of Technology, Pasadena, California 91125 a n d the TlDepartment of Chemistry a n d Biochemistry, University of California, Los Angeles, California 90024
The rate of glutamine synthesis was fastest after growth in media deficient in free ammonium ion, whereas it was slowestfollowing growth in media containing both glutamic acid and glutamine.The reverse trend was observed for the biosynthesis of alanine
We report here the use of ”N-NMR to study the influence of different nitrogen sources in the medium on the relative rates of biosynthesis of glutamine and alaninein intact N. crassa and the concomitantinformation the results provide as to theregulation of these pathways in uiuo
Summary
Consequence is that the raotef utilization of y-I5Nof glutamine for the biosynthesis of other metabolites must be slow com-. Glutamine synthesis is only repressed significantly when both glutamic acid and glutamine are present in the preincubation medium The culture grown on glutamine, which can provide two nitrogens/molecule, has an intermediate rate of glutamine synthesis, comparable to that observed in mycelia grown on ammonium nitrate (Table I). These results suggest that significant enhancement of glutamine synthesis occurs when the preincubation medium is deficient in free ammonium ion or in alternative preferred nitrogen sources, such as glutamine.
Sign-in/Register to view highlights & summary 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 callDisclaimer: 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.
