Purine Degradation and Ureide Catabolism by Soybean (Glycine Max (L.) Merrill); Cell Suspension Cultures
Stahlhut, Roy William
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https://hdl.handle.net/2142/71644
Description
Title
Purine Degradation and Ureide Catabolism by Soybean (Glycine Max (L.) Merrill); Cell Suspension Cultures
Author(s)
Stahlhut, Roy William
Issue Date
1987
Doctoral Committee Chair(s)
Widholm, Jack M.
Department of Study
Agronomy
Discipline
Agronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Plant Physiology
Abstract
The purine degradation pathway and ureide catabolism were studied in a soybean (Glycine max (L.) Merrill) cell suspension capable of growth on the ureides allantoin and allantoic acid, and their purine precursors uric acid and inosine-5$\sp\prime$-mono- phosphate (IMP), as sole nitrogen sources. The inhibitors of purine degradation, allantoxanamide and allopurinol, caused accumulation of uric acid and hypoxanthine, respectively, in cell suspensions fed radiolabelled IMP and effectively blocked growth on IMP, but not allantoin, as a sole nitrogen source.
Enzymes for ureide catabolism (allantoinase, allantoate amidohydrolase) and assimilation (glutamine synthetase, glutamate synthase, glutamate dehydrogenase, aminotransferases, serine transhydroxymethylase) were assayed. Allantoinase activity levels were similar in cell suspensions growing on allantoin or NH$\sb4\sp+$/NO$\sb3\sp-$ as nitrogen sources, while allantoate amidohydrolase activity was lower in cells grown on NH$\sb4\sp+$/NO$\sb3\sp-$, but inducible to higher levels by allantoin or ureide precursors.
Feeding cell suspension (7-$\sp $C) and (4,5-$\sp $C) allantoin allowed identification of the end products of ureide catabolism. Label from (7-$\sp $C) allantoin (urea moiety) was released as CO$\sb2$, while label from (4,5-$\sp $C) allantoin (glyoxylate moiety) was incorporated into glycine and serine.
Urea was not found to be an intermediate in ureide catabolism to ammonium and CO$\sb2$ based upon studies comparing the effect of the urease inhibitors phenylphosphorodiamidate and acetohydroxamate on cell growth and catabolism of (7-$\sp $C) allantoin versus ($\sp $C) urea. These inhibitors have no effect on allantoin catabolism, but are inhibitory to urea catabolism. Nickel was also found to be essential for urea, but not allantoin catabolism.
The exact pathway from allantoic acid to glyoxylate was not determined due to our inability to detect intermediate compounds. The nonphysiological ureide analog, hydantoic acid, was found to be an excellent nitrogen source for soybean cell suspension growth and an alternate substrate to allantoic acid for in vitro enzymic ammonium release. The entire allantoate molecule may be catabolized by the enzyme allantoate amidohydrolase, or possibly, a separate amidohydrolase.
The purine degradation pathway of soybean cell suspensions was similar to the pathway reported in higher plant tissues and nodules of the soybean-Bradyrhizobium symbiosis.
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