5-Phosphoribosylpyrophosphate amidotransferase from soybean root nodules: kinetic and regulatory properties

Archives of Biochemistry and Biophysics
P H ReynoldsD D Randall

Abstract

Most of the nitrogen transported from the nodules of nitrogen-fixing soybean plants is in the form of the ureides allantoin and allantoic acid. Recent work has shown that ureides are formed in the plant fraction of the nodule from de novo purine biosynthesis and purine oxidation. 5-Phosphoribosylpyrophosphate amidotransferase (PRAT), which catalyzes the first committed step of purine biosynthesis, has been purified 1500-fold from soybean root nodules. The enzyme had an apparent Mr of 8 X 10(6), but this estimate may have been for an aggregation of several purine biosynthetic activities. PRAT showed a pH optimum of pH 8.0, and Km values were 18 and 0.4 mM for glutamine and 5-phosphoribosyl-1-pyrophosphate (PRPP), respectively. The reaction required Mg2+, and PRPPMg3- was shown to be the reactive molecular species of PRPP. Ammonia could replace glutamine as a substrate, and the Vm with ammonia was twice that obtained when glutamine was the substrate. The initial-rate kinetics showed sequential addition of substrates to the enzyme. Product inhibition data was consistent with the order of product release being phosphoribosylamine, PPi, and glutamate. The enzyme was subject to regulation by end products of the purine biosynthetic pa...Continue Reading

References

Sep 1, 1976·Analytical Biochemistry·G L King, E W Holmes
Jan 1, 1983·Archives of Biochemistry and Biophysics·M J Boland, K R Schubert
Aug 1, 1953·The Biochemical Journal·M DIXON
Sep 1, 1979·Plant Physiology·P R McClure, D W Israel
Jun 1, 1982·Plant Physiology·P H ReynoldsD D Randall

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Citations

Jul 13, 2013·Journal of Plant Physiology·Gregorio Gálvez-ValdiviesoManuel Pineda
Feb 1, 1986·Proceedings of the National Academy of Sciences of the United States of America·S HenikoffD Patterson
Jul 13, 2002·Plant Physiology·Penelope M C SmithCraig A Atkins
May 4, 2006·Annual Review of Plant Biology·Rita ZrennerRalf Boldt
Dec 9, 2003·Journal of Plant Physiology·Claudio StasollaHiroshi Ashihara
Jul 16, 2013·Plant Science : an International Journal of Experimental Plant Biology·Xiao-Rong ShuiJian-Xiong Li
Jan 1, 1987·BioEssays : News and Reviews in Molecular, Cellular and Developmental Biology·S Henikoff

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