page_title: Aminoacylase
section_title: Enzyme Mechanism
hierarchical_section_title: Aminoacylase / Enzyme Mechanism
caption_attribution_description: English: Aminoacylase Reaction Mechanism
context_page_description: In enzymology, an aminoacylase is an enzyme that catalyzes the chemical reaction
  N-acyl-L-amino acid + H₂O ⇌ carboxylate + L-amino acid
  Thus, the two substrates of this enzyme are N-acyl-L-amino acid and H₂O, whereas its two products are carboxylate and L-amino acid.
  This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in linear amides. The systematic name of this enzyme class is N-acyl-L-amino acid amidohydrolase. Other names in common use include dehydropeptidase II, histozyme, hippuricase, benzamidase, acylase I, hippurase, amido acid deacylase, L-aminoacylase, acylase, aminoacylase I, L-amino-acid acylase, alpha-N-acylaminoacid hydrolase, long acyl amidoacylase, and short acyl amidoacylase. This enzyme participates in urea cycle and metabolism of amino groups.
context_section_description: Aminoacylase is a metallo-enzyme that needs Zinc (Zn²⁺) as a cofactor to function. The Zinc ions inside of aminoacylase are each coordinated to histidine, glutamate, aspartate, and water. The Zinc ion polarizes the water, facilitating its deprotonation by a nearby basic residue. The negatively charged hydroxide ion is nucleophilic and attacks the electrophilic carbonyl carbon of the substrate's acyl group. The exact mechanism after this point is unknown, with one possibility being that the carbonyl then reforms, breaks the amide bond, and forms the two products. At some point in the mechanism, another water molecule enters and coordinates with Zinc, returning the enzyme to its original state.
  The nucleophilic attack by water is the rate-limiting step of aminoacylase's catalytic mechanism. This nucleophilic attack is reversible while the subsequent steps are fast and irreversible. This reaction sequence is an example of Michaelis–Menten kinetics, allowing one to determine KM, Kcat, Vₘₐₓ, turnover number, and substrate specificity through classic Michaelis-Menten enzyme experiments. The second and third forward steps cause the formation and release of the reaction's products.
caption: Aminoacylase Reaction Mechanism (click for larger image)
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