Histidine ammonia-lyase

Histidine ammonia-lyase (HAL), also known as histidase, is an enzyme that catalyzes the deamination of histidine to urocanic acid and ammonia. This enzyme plays a crucial role in the metabolism of histidine, an essential amino acid in many organisms.

Structure

Histidine ammonia-lyase is a tetramer composed of identical subunits. Each subunit contains a pyridoxal phosphate (PLP) cofactor, which is essential for the enzyme's catalytic activity. The enzyme's structure is characterized by a large, central, eight-stranded beta-sheet surrounded by alpha-helices.

Function

Histidine ammonia-lyase is primarily involved in the catabolism of histidine. It catalyzes the first step in this process, converting histidine to urocanic acid and ammonia. This reaction is a key part of the histidine degradation pathway, which allows organisms to use histidine as a source of energy and to recycle its components for other purposes.

Clinical significance

Mutations in the gene encoding histidine ammonia-lyase can lead to a rare metabolic disorder known as histidinemia. This condition is characterized by elevated levels of histidine and histamine in the blood and urine, and can cause a variety of symptoms including intellectual disability, speech impairment, and growth retardation.

See also

• Histidinemia
• Histidine metabolism
• Urocanic acid
• Ammonia

References

‎

---

Translate: - East Asian 中文, 日本, 한국어, South Asian हिन्दी, தமிழ், తెలుగు, Urdu, ಕನ್ನಡ, Southeast Asian Indonesian, Vietnamese, Thai, မြန်မာဘာသာ, বাংলা
European español, Deutsch, français, Greek, português do Brasil, polski, română, русский, Nederlands, norsk, svenska, suomi, Italian
Middle Eastern & African عربى, Turkish, Persian, Hebrew, Afrikaans, isiZulu, Kiswahili,
Other Bulgarian, Hungarian, Czech, Swedish, മലയാളം, मराठी, ਪੰਜਾਬੀ, ગુજરાતી, Portuguese, Ukrainian