Definition

1. Noun:
   • An essential amino acid: Histidine is one of the amino acids that the human body cannot synthesize on its own and must obtain from the diet.
   • Found in proteins: It is a standard component of most proteins.
   • Important for biological functions: It is crucial for the growth and repair of tissues, and plays roles in various metabolic processes.

Usage Examples

• Noun:
  • Histidine is required for proper growth in infants and children.
  • Many protein-rich foods, such as meat, fish, and dairy, are good sources of histidine.
  • A deficiency in histidine can impair tissue repair.

Advanced Usage

• Biochemical Context: In biochemistry, histidine is noted for having an imidazole side chain, which allows it to act as a proton donor or acceptor. This makes it a common catalytic residue in enzyme active sites.
  • The enzyme's activity depends on a critical histidine residue in its active site.
• Medical/Nutritional Context: It is classified as an "essential" amino acid for humans, meaning it must be consumed.
  • Histidine supplementation is sometimes considered in specific clinical nutrition plans.

Variants and Related Words

• L-histidine (n): The specific, naturally occurring form (isomer) of histidine found in proteins.
• Histidinemia (n): A rare metabolic disorder characterized by elevated levels of histidine in the blood.

Synonyms

• Essential amino acid: This is its category, not a direct synonym. Other specific essential amino acids include , , and .

Related Phrases and Compounds

• Histidine decarboxylase: An enzyme that converts histidine into histamine.
• Histidine kinase: A type of enzyme involved in signal transduction in many organisms.
• Histidine-rich glycoprotein: A specific protein that contains a high proportion of histidine residues.

(Note: As 'histidine' is a specific biochemical noun, it does not have phrasal verbs or idioms associated with its common usage.)

Noun

1. an essential amino acid found in proteins that is important for the growth and repair of tissue