text: Purines from turnover of cellular nucleic acids (or from food) can also be salvaged and reused in new nucleotides.
  * The enzyme adenine phosphoribosyltransferase (APRT) salvages adenine. 
  * The enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) salvages guanine and hypoxanthine. (Genetic deficiency of HGPRT causes Lesch–Nyhan syndrome.)