Carbamoyl phosphate

Definition

Carbamoyl phosphate is a crucial intermediate in the urea cycle, formed from ammonia and bicarbonate, catalyzed by the enzyme carbamoyl phosphate synthetase I. This molecule plays a significant role in nitrogen metabolism, helping to convert excess nitrogen into urea for excretion. By linking amino acid catabolism to the urea cycle, carbamoyl phosphate ensures that toxic ammonia is efficiently detoxified.

5 Must Know Facts For Your Next Test

1. Carbamoyl phosphate is synthesized in the mitochondria of liver cells and is the first step in the urea cycle.
2. The reaction to form carbamoyl phosphate requires two ATP molecules, making it an energy-consuming step.
3. Carbamoyl phosphate can also enter the pyrimidine synthesis pathway, linking nitrogen metabolism with nucleotide synthesis.
4. Deficiency in carbamoyl phosphate synthetase I can lead to hyperammonemia, a condition characterized by elevated levels of ammonia in the blood.
5. The regulation of carbamoyl phosphate production is influenced by substrate availability, especially ammonia and ATP levels.

Review Questions

• How does carbamoyl phosphate contribute to the detoxification of ammonia in the body?
  • Carbamoyl phosphate is essential for converting toxic ammonia into urea through the urea cycle. It is formed when ammonia combines with bicarbonate, catalyzed by carbamoyl phosphate synthetase I. This process helps to prevent ammonia accumulation in the body, which can be harmful. By facilitating this conversion, carbamoyl phosphate ensures that excess nitrogen from amino acid catabolism is efficiently eliminated.
• What are the consequences of a deficiency in carbamoyl phosphate synthetase I on nitrogen metabolism?
  • A deficiency in carbamoyl phosphate synthetase I disrupts the formation of carbamoyl phosphate, leading to impaired urea cycle function. This results in an accumulation of ammonia in the bloodstream, a condition known as hyperammonemia. High levels of ammonia can be neurotoxic and lead to serious health issues such as lethargy, confusion, and even coma. Therefore, proper functioning of this enzyme is crucial for maintaining safe levels of nitrogen waste in the body.
• Evaluate how the role of carbamoyl phosphate links amino acid catabolism and energy metabolism in humans.
  • Carbamoyl phosphate serves as a pivotal link between amino acid catabolism and energy metabolism through its role in both the urea cycle and pyrimidine synthesis. When proteins are broken down, excess nitrogen is released as ammonia. Carbamoyl phosphate converts this ammonia into urea for safe excretion. Additionally, it can enter pathways for synthesizing nucleotides, which are essential for DNA and RNA. This dual functionality illustrates how nitrogen metabolism is interconnected with overall energy metabolism and nucleotide synthesis, emphasizing its importance in cellular function.

Related terms

Urea: A waste product formed in the liver from the breakdown of proteins, excreted by the kidneys.

Carbamoyl Phosphate Synthetase I: An enzyme that catalyzes the formation of carbamoyl phosphate from ammonia and bicarbonate, an essential step in the urea cycle.

Ornithine: An amino acid that acts as a carrier in the urea cycle, facilitating the conversion of carbamoyl phosphate into citrulline.