Ribose-5-phosphate isomerase

Ribose-5-phosphate isomerase (RPI) is an enzyme that plays a crucial role in the pentose phosphate pathway (PPP), a metabolic pathway parallel to glycolysis. It catalyzes the interconversion between ribose 5-phosphate (R5P) and ribulose 5-phosphate (Ru5P), two pentose sugars that are essential for various biochemical processes. This reaction is important for the synthesis of nucleotides and nucleic acids, as well as for the production of ribose, which is a component of ATP and other critical biomolecules.

Function

The primary function of RPI is to facilitate the reversible conversion of R5P to Ru5P. This reaction is vital in the PPP, which is not only a source of NADPH for reductive biosynthesis but also provides ribose sugar for nucleotide synthesis. The PPP operates in all living cells, providing the necessary components for the synthesis of DNA and RNA, as well as for antioxidant defense mechanisms.

Structure

RPI is a monomeric enzyme that can be found in both prokaryotic and eukaryotic organisms. Its structure has been resolved through X-ray crystallography, revealing a fold that is common among enzymes of the isomerase family. The active site of RPI contains residues that are essential for catalysis and substrate binding.

Clinical Significance

Mutations in the gene encoding RPI are associated with Ribose-5-phosphate isomerase deficiency, a rare metabolic disorder. This condition is characterized by a variety of symptoms, including developmental delay, seizures, and other neurological impairments. Due to the enzyme's role in nucleotide synthesis, its deficiency can have profound effects on cellular function and development.

See Also

• Pentose phosphate pathway
• Metabolism
• Enzyme
• Nucleotide
• X-ray crystallography