Asparagine synthase

As a third example of a coupled reaction consider the following ligase reaction catalyzed by asparagine synthase (glutamine hydrolyzing) that has eight reactants ... 

Now consider the asparagine synthase (glutamine hydrolyzing) reaction from the viewpoint of the further transformed Gibbs energy G. The oxygen row and the h2o column are omitted to obtain... 

Several aaRS-like proteins are involved in metabobc pathways (1). For example, E. coli asparagine synthase, an aspartyl-tRNA synthetase (AspRS)-like enzyme, catalyzes the synthesis of asparagine from aspartate and ATP. A paralog of LysRS-II, called PoxA/GenX, is important for pyruvate oxidase activity in E. coli and Salmonella typhimurium and for virulence in S. typhimurium. The E. coli biotin synthetase/repressor protein (BirA), which has a domain that resembles structurally the seryl-tRNA synthetase (SerRS) catalytic domain, activates biotin to modify posttranslationaUy various metabolic proteins involved in carboxylation and decarboxylation. BirA can also bind DNA and regulate its own transcription using biotin as a corepressor. A histidyl-tRNA synthetase (HisRS)-hke protein from Lactococcus lactis, HisZ is involved in the allosteric activation of the phosphoribosyl-transferase reaction. 

The enzyme asparagine synthase catalyzes the ATP, requiring the transamidation reaction shown below ... 

Asparagine, the amide of aspartate, is not formed directly from aspartate and NHj. Instead, the amido group of glutamine is transferred by amido group transfer during an ATP-requiring reaction catalyzed by asparagine synthase ... 

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