X-His dipeptidase

Enzyme involved in peptide metabolism

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X-His dipeptidase, also known as prolidase, is an enzyme that plays a crucial role in the metabolism of dipeptides containing a C-terminal histidine residue. This enzyme is part of the peptidase family and is involved in the final stages of protein digestion and turnover.

Structure

Structure of X-His dipeptidase

X-His dipeptidase is a metalloenzyme that requires divalent metal ions, such as manganese or zinc, for its catalytic activity. The enzyme is typically a homodimer, meaning it consists of two identical subunits. Each subunit contains a metal-binding site that is essential for its enzymatic function.

Function

The primary function of X-His dipeptidase is to hydrolyze dipeptides with a C-terminal histidine, releasing free histidine and the corresponding amino acid. This activity is important for the recycling of amino acids and the regulation of histidine levels in the body. The enzyme is particularly active in tissues with high rates of protein turnover, such as the liver and kidney.

Mechanism

X-His dipeptidase catalyzes the hydrolysis of the peptide bond in dipeptides. The metal ion in the active site plays a critical role in stabilizing the transition state and activating a water molecule, which acts as a nucleophile to attack the carbonyl carbon of the peptide bond. This results in the cleavage of the bond and the release of free amino acids.

Clinical significance

Deficiency or malfunction of X-His dipeptidase can lead to metabolic disorders. For example, prolidase deficiency is a rare genetic disorder characterized by the accumulation of imidodipeptides in the body, leading to symptoms such as skin lesions, recurrent infections, and developmental delay. Understanding the function and regulation of this enzyme is important for diagnosing and treating such conditions.

Related pages

• Peptidase
• Histidine
• Metalloenzyme
• Prolidase deficiency