* A nuclease frees the nucleotide
** A nucleotidase creates adenosine, then adenosine deaminase creates inosine
** Alternatively, AMP deaminase creates inosinic acid, then a nucleotidase creates inosine
* Purine nucleoside phosphorylase acts upon inosine to create hypoxanthine
* Xanthine oxidase catalyzes the biotransformation of hypoxanthine to xanthine
* Xanthine oxidase acts upon xanthine to create uric acid