Hypoxanthine

Hypoxanthine is a naturally occurring purine base produced during adenine and guanine metabolism. Cells reuse it in nucleotide salvage pathways to make inosine and adenine nucleotides.

Hypoxanthine-guanine phosphoribosyltransferase: An enzyme that transfers phosphoribosyl from PRPP to hypoxanthine or guanine, forming nucleotide monophosphates. It salvages hypoxanthine directly into inosine monophosphate.
Purine: A two-ring nitrogen-containing molecular scaffold found in nucleic acids and other biomolecules. Hypoxanthine is one modified member of this chemical family.
Lesch–Nyhan syndrome: An X-linked disorder caused by near-complete deficiency of hypoxanthine-guanine phosphoribosyltransferase. Impaired hypoxanthine salvage contributes to excess uric acid and neurological symptoms.
Wobble base pairing: Nonstandard pairing at the third codon position that allows some tRNAs to recognize multiple codons. Hypoxanthine in inosine can pair with several RNA bases in wobble positions.
Inosine monophosphate: A purine nucleotide that serves as a precursor to AMP and GMP. Hypoxanthine becomes this nucleotide in the principal salvage reaction.
Nucleobase: A nitrogen-containing molecule that forms the information-bearing bases of nucleic acids. Hypoxanthine is a purine nucleobase, though not a standard DNA or RNA base.
Kelley–Seegmiller syndrome: A disorder caused by partial deficiency of hypoxanthine-guanine phosphoribosyltransferase. Reduced salvage leaves more hypoxanthine available for degradation to uric acid.
DNA mismatch repair: A pathway that detects and corrects mismatched bases introduced during DNA replication. Hypoxanthine formed by adenine deamination can be recognized as a DNA lesion.
Purine nucleoside phosphorylase: An enzyme that reversibly cleaves purine nucleosides into bases and ribose-1-phosphate. It generates hypoxanthine by cleaving inosine.
Inosine: A nucleoside composed of hypoxanthine linked to ribose. It is the ribose-containing form from which hypoxanthine can be released.

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