Arginase

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Enzyme involved in the urea cycle

Arginase

Arginase is an enzyme that catalyzes the hydrolysis of arginine to ornithine and urea. This reaction is a key step in the urea cycle, which is essential for the detoxification of ammonia in the liver.

Structure

Arginase exists in two isoforms: Arginase 1 (ARG1) and Arginase 2 (ARG2). ARG1 is primarily found in the cytosol of hepatocytes, while ARG2 is located in the mitochondria of various tissues, including the kidney and prostate.

Function

The primary function of arginase is to catalyze the final step of the urea cycle, converting arginine into ornithine and urea. This process is crucial for the removal of excess nitrogen from the body. In addition to its role in the urea cycle, arginase also plays a part in the regulation of nitric oxide synthesis by competing with nitric oxide synthase for their common substrate, arginine.

Clinical Significance

Deficiency in arginase can lead to a rare disorder known as argininemia, characterized by elevated levels of arginine in the blood. Symptoms of argininemia include spasticity, ataxia, and intellectual disability. Diagnosis is typically confirmed through genetic testing and measurement of enzyme activity.

Regulation

Arginase activity is regulated by various factors, including diet, hormones, and cytokines. For instance, glucocorticoids and insulin can upregulate arginase expression, while inflammatory cytokines such as interleukin-4 (IL-4) and interleukin-13 (IL-13) can also enhance its activity.

Research

Recent studies have explored the role of arginase in various diseases, including cardiovascular disease, cancer, and asthma. Inhibitors of arginase are being investigated as potential therapeutic agents for these conditions.

See also

• Urea cycle
• Ornithine
• Nitric oxide synthase
• Argininemia