key term - Hypoxanthine-guanine phosphoribosyltransferase (hgprt)

Definition

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) is an enzyme that plays a critical role in the purine salvage pathway, which recycles purines to generate nucleotides for DNA and RNA synthesis. It catalyzes the transfer of a phosphoribosyl group from 5-phosphoribosyl-1-pyrophosphate (PRPP) to hypoxanthine or guanine, converting them into inosine monophosphate (IMP) and guanosine monophosphate (GMP), respectively. This process helps to maintain adequate levels of purines in cells, preventing the need for de novo synthesis, which can be energetically expensive.

5 Must Know Facts For Your Next Test

1. HGPRT deficiency leads to Lesch-Nyhan syndrome, a genetic disorder characterized by neurological problems and self-injurious behavior due to impaired purine metabolism.
2. HGPRT operates efficiently at low concentrations of substrates, demonstrating its effectiveness in the recycling process within cells.
3. The enzyme helps prevent excessive uric acid production, thus playing a role in preventing gout, a condition caused by uric acid crystal accumulation.
4. HGPRT can utilize both hypoxanthine and guanine as substrates, showcasing its versatility in nucleotide metabolism.
5. Mutations in the HGPRT gene can result in various metabolic disorders, highlighting its importance in maintaining purine balance in the body.

Review Questions

• How does HGPRT contribute to the efficiency of nucleotide metabolism in cells?
  • HGPRT contributes to nucleotide metabolism by facilitating the recycling of purines through the salvage pathway. This allows cells to efficiently produce nucleotides from available hypoxanthine and guanine instead of relying solely on de novo synthesis, which requires more energy and resources. By converting these bases into nucleotides like IMP and GMP, HGPRT helps maintain balanced nucleotide pools necessary for DNA and RNA synthesis.
• Discuss the implications of HGPRT deficiency on human health and its associated conditions.
  • HGPRT deficiency can lead to Lesch-Nyhan syndrome, which is marked by neurological symptoms and behavioral issues due to an inability to recycle purines effectively. This deficiency results in an increase of uric acid levels, leading to potential complications like gout and kidney stones. Understanding this relationship is crucial for developing therapies for individuals affected by HGPRT deficiency and managing associated health risks.
• Evaluate how mutations in the HGPRT gene can affect overall purine metabolism and influence disease states.
  • Mutations in the HGPRT gene can severely disrupt purine metabolism by reducing or eliminating enzyme activity. This disruption can lead to an accumulation of uric acid and decreased levels of important nucleotides. The resulting metabolic imbalance is linked not only to conditions like Lesch-Nyhan syndrome but also contributes to increased susceptibility to other disorders related to nucleotide synthesis and degradation. Analyzing these mutations provides insight into their broad effects on cellular function and disease progression.

Related terms

Purine Salvage Pathway: A metabolic pathway that recycles purines from degraded nucleic acids to synthesize nucleotides, allowing cells to conserve resources.

Adenine: A purine nucleotide that is a building block of DNA and RNA, also serving as an energy carrier in the form of ATP.

Xanthine Oxidase: An enzyme that catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid, playing a key role in purine catabolism.