Adenosine kinase

An enzyme involved in the metabolism of adenosine

Adenosine kinase is an enzyme that plays a crucial role in the metabolism of adenosine, a nucleoside that is involved in various physiological processes. This enzyme is responsible for the phosphorylation of adenosine to form adenosine monophosphate (AMP), a key step in the salvage pathway of adenine nucleotides.

Structure

Adenosine kinase is a protein that is encoded by the ADK gene in humans. The enzyme is composed of a single polypeptide chain and has a molecular weight of approximately 40 kDa. The structure of adenosine kinase has been elucidated through X-ray crystallography, revealing a complex fold that is typical of nucleotide-binding proteins. The active site of the enzyme is located in a cleft between two domains, where adenosine and ATP bind during the catalytic process.

Function

The primary function of adenosine kinase is to catalyze the transfer of a phosphate group from ATP to adenosine, forming AMP. This reaction is crucial for maintaining the balance of adenosine levels within the cell. Adenosine itself is a signaling molecule that can influence various physiological processes, including vasodilation, neurotransmission, and immune response. By converting adenosine to AMP, adenosine kinase regulates the availability of adenosine for these processes.

Regulation

Adenosine kinase activity is regulated by several factors, including the availability of its substrates, adenosine and ATP. The enzyme is also subject to feedback inhibition by its product, AMP. Additionally, adenosine kinase expression and activity can be modulated by various physiological and pathological conditions, such as hypoxia, inflammation, and cancer.

Clinical significance

Alterations in adenosine kinase activity have been implicated in several diseases. For example, reduced activity of adenosine kinase can lead to elevated levels of adenosine, which may contribute to the pathophysiology of epilepsy, chronic pain, and inflammatory disorders. Conversely, increased activity of the enzyme can decrease adenosine levels, potentially affecting cardiovascular and neurological functions.

Research

Adenosine kinase is a target of interest in drug development, particularly for conditions where modulation of adenosine levels could be therapeutic. Inhibitors of adenosine kinase are being explored for their potential to increase adenosine levels and provide benefits in conditions such as stroke, myocardial infarction, and neurodegenerative diseases.

Related pages

• Adenosine triphosphate
• Nucleotide metabolism
• Enzyme kinetics
• Signal transduction

Gallery

• 
  Crystal structure of adenosine kinase