Carbamoyl phosphate synthetase ii (cps ii)

Definition

Carbamoyl phosphate synthetase II (CPS II) is a key enzyme in the pyrimidine biosynthesis pathway, responsible for the synthesis of carbamoyl phosphate from bicarbonate, ammonia, and ATP. This reaction represents the first committed step in pyrimidine nucleotide production, linking nitrogen metabolism and nucleic acid synthesis.

5 Must Know Facts For Your Next Test

1. CPS II is located in the cytoplasm, distinguishing it from CPS I, which is found in the mitochondria and is involved in urea cycle metabolism.
2. The regulation of CPS II is tightly controlled by various metabolites, including UTP and PRPP, which act as feedback inhibitors and activators respectively.
3. CPS II uses bicarbonate as a substrate instead of carbon dioxide, making it distinct from CPS I in its mechanism.
4. The activity of CPS II is essential for rapidly dividing cells, such as those in the bone marrow and the immune system, where nucleotide synthesis is crucial.
5. CPS II is an allosteric enzyme that can be influenced by multiple signals reflecting the cellular environment and needs for pyrimidines.

Review Questions

• How does CPS II contribute to the regulation of pyrimidine biosynthesis?
  • CPS II serves as the first committed step in the pyrimidine biosynthesis pathway, thus playing a critical role in regulating the overall production of pyrimidines. It is influenced by various metabolites such as UTP, which inhibits its activity when there is an abundance of pyrimidines, ensuring that nucleotide synthesis aligns with cellular needs. Conversely, PRPP acts as an activator, signaling the demand for more pyrimidine nucleotides during periods of active growth or DNA synthesis.
• Discuss how CPS II differs from CPS I in terms of location and substrate usage.
  • CPS II is located in the cytoplasm while CPS I resides in the mitochondria. One significant difference between them is their substrates; CPS II utilizes bicarbonate as a substrate instead of carbon dioxide, which is used by CPS I. This difference highlights their roles in different metabolic pathways—CPS II focuses on nucleotide synthesis while CPS I plays a crucial role in the urea cycle.
• Evaluate the implications of CPS II's activity on rapidly dividing cells and potential therapeutic targets.
  • CPS II activity is particularly crucial for rapidly dividing cells like those in cancer or immune response scenarios since these cells have an increased demand for nucleotides for DNA synthesis. Understanding how CPS II functions and its regulatory mechanisms opens up potential therapeutic avenues; inhibitors of CPS II could be designed to limit nucleotide availability for tumor cells, thereby slowing their proliferation. This approach could be a part of targeted cancer therapies aimed at disrupting metabolic pathways vital for tumor growth.

Related terms

Pyrimidine: A type of nitrogenous base that includes cytosine, thymine, and uracil, which are essential components of DNA and RNA.

Urate: A product of purine metabolism that can inhibit CPS II activity, thus connecting purine and pyrimidine metabolism.

Aspartate transcarbamoylase (ATCase): An enzyme that catalyzes the reaction between carbamoyl phosphate and aspartate to form carbamoyl aspartate, furthering pyrimidine biosynthesis.