Question related to L-arginine biosynthesis With respect to the L-arginine Biosynthesis pathway, the very first reaction converts L-glutamate to N-acetyl L-glutamate. In the linked reaction scheme, why are only L-glutamate and N-acetyl glutamate considered, and not acetyl-CoA or the coenzyme? Is this because L-glutamate and N-acetyl L-glutamate are the main compounds to be considered? Why are they the main compounds being considered? Are these two compounds (L-glutamate and N-acetyle L-glutamate) the ligands?

The synthesis of N-acetylglutamate is mediated by the enzyme _N-acetylglutamate synthase_. This enzyme has **L-glutamate as its substrate** and uses **acetyl-coenzyme A** as a co-enzyme **acetyl donor**. Acetylcoenzyme A (Acetyl-CoA) is generally abbreviated in structural formulas, because it is a relatively complex molecule. The only thing of relevance is the acetyl group which is transferred from a thiol group to L-glutamate.

Note that _ligands_ is a term reserved for molecules binding to receptors; _substrates_ is the proper term for intermediates in enzymatic reactions.

!N-acetylglutamate
N-acetylglutamate synthesis. Source: The Medical Biochemistry page