Caulobacter crescentus CB15 Pathway: ammonia assimilation cycle III

Pathway diagram: ammonia assimilation cycle III

If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Locations of Mapped Genes:

Schematic showing all replicons, marked with selected genes

Synonyms: ammonia assimilation III, GS/GOGAT pathway

Superclasses: Degradation/Utilization/Assimilation Inorganic Nutrients Metabolism Nitrogen Compounds Metabolism Ammonia Assimilation

Escherichia coli K-12 can synthesize L-glutamate from ammonia in two pathways. In addition, if complex sources of nitrogen are available, other pathways become active and take over glutamate synthesis.

In the first pathway L-glutamate is synthesized directly from ammonia, 2-oxoglutarate, and NADPH, as described in glutamate biosynthesis III.

The other pathway, which is described here, is a cyclic pathway, which consists of two steps.

In the first step L-glutamine is synthesized from ammonia and L-glutamate in an ATP-requiring reaction.

ammonium + L-glutamate + ATP → L-glutamine + ADP + phosphate + H+ (EC

In the second step the amido group is transferred from L-glutamine to 2-oxoglutarate yielding two molecules of L-glutamate.

2 L-glutamate + NADP+ ← L-glutamine + 2-oxoglutarate + NADPH + H+ (EC

Because glutamine biosynthesis utilizes one molecule of glutamate and the second reaction yields 2 molecules of glutamate, these two reactions function as a cycle, each turn of which utilizes one molecule each of ammonia, ATP, NADPH, and 2-oxoglutarate, and produces one molecule of L-glutamate.

This pathway is active in energy-rich (glucose-containing), nitrogen-poor environments.

Subpathways: glutamate biosynthesis I , glutamine biosynthesis I

Created in MetaCyc 02-Dec-1998 by Marine Biological Laboratory
Imported from MetaCyc 18-Sep-2013 by Fulcher CA , SRI International

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Page generated by SRI International Pathway Tools version 19.0 on Tue Oct 6, 2015, biocyc13.