Human Adenine Phosphoribosyltransferase
[APT_HUMAN] Defects in APRT are the cause of adenine phosphoribosyltransferase deficiency (APRTD) [MIM:614723]; also known as 2,8-dihydroxyadenine urolithiasis. An enzymatic deficiency that can lead to urolithiasis and renal failure. Patients have 2,8-dihydroxyadenine (DHA) urinary stones.       
[APT_HUMAN] Catalyzes a salvage reaction resulting in the formation of AMP, that is energically less costly than de novo synthesis.
Publication Abstract from PubMed
In mammals, adenine phosphoribosyltransferase (APRT, EC 18.104.22.168) is present in all tissues and provides the only known mechanism for the metabolic salvage of adenine resulting from the polyamine biosynthesis pathway or from dietary sources. In humans, APRT deficiency results in serious kidney illness such as nephrolithiasis, interstitial nephritis, and chronic renal failure as a result of 2,8-dihydroxyadenine (DHA) precipitation in the renal interstitium. To address the molecular basis of DHA-urolithiasis, the recombinant human APRT was crystallized in complex with adenosine 5'-monophosphate (AMP). Refinement of X-ray diffraction data extended to 2.1 A resolution led to a final crystallographic R(factor) of 13.3% and an R(free) of 17.6%. This structure is composed of nine beta-strands and six alpha-helices, and the active site pocket opens slightly to accommodate the AMP product. The core of APRT is similar to that of other phosphoribosyltransferases (PRTases), although the adenine-binding domain is quite different. Structural comparisons between the human APRT and other "type I" PRTases of known structure revealed several important features of the biochemistry of PRTases. We propose that the residues located at positions corresponding to Leu159 and Ala131 in hAPRT are responsible for the base specificities of type I PRTases. The comparative analysis shown here also provides structural information for the mechanism by which mutations in the human APRT lead to DHA-urolithiasis.
Three-dimensional structure of human adenine phosphoribosyltransferase and its relation to DHA-urolithiasis.,Silva M, Silva CH, Iulek J, Thiemann OH Biochemistry. 2004 Jun 22;43(24):7663-71. PMID:15196008
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.