Adenine phosphoribosyltransferase (APRTase) is an enzyme encoded by the APRTgene, found in humans on chromosome 16.[5] It is part of the Type I PRTase family and is involved in the nucleotide salvage pathway, which provides an alternative to nucleotide biosynthesis de novo in humans and most other animals.[6] In parasitic protozoa such as giardia, APRTase provides the sole mechanism by which AMP can be produced.[7] APRTase deficiency contributes to the formation of kidney stones (urolithiasis) and to potential kidney failure.[8]