ISSN:
1432-2048
Keywords:
Glutamate synthase
;
Glutamine synthetase
;
Nitrogen fixation
;
Phaseolus (glutamate synthase)
;
Plastid (glutamate synthase)
;
Root nodule
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The two isoenzymes of NADH-dependent glutamate synthase (NADH-GOGAT; EC 1.4.1.14), previously identified in root nodules of Phaseolus vulgaris L., have both been shown to be located in root-nodule plastids. The nodule specific NADH-GOGAT II accounts for the majority of the activity in root nodules, and is present almost exclusively in the central tissue of the nodule. However about 20% of NADH-GOGAT I activity is present in the nodule cortex, at about the same specific activity as this isoenzyme is found in the central tissue. Glutamine synthetase (GS; EC 6.3.1.2) occurs predominantly as the γ polypeptide in the central tissue, whereas in the cortex, the enzyme is represented mainly by the β polypeptide. Over 90% of both GS and NADH-GOGAT activities are located in the central tissue of the nodule and GS activity exceeds NADH-GOGAT activity by about twofold in this region. Using the above information, a model for the subcellular location and stoichiometry of nitrogen metabolism in the central tissue of P. vulgaris root nodules is presented.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00397583
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