Human Adenine Phosphoribosyltransferase Complexed with PRPP, ADE and R5P
[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
Adenine phosphoribosyltransferase (APRT) is an important enzyme component of the purine recycling pathway. Parasitic protozoa of the order Kinetoplastida are unable to synthesize purines de novo and use the salvage pathway for the synthesis of purine bases rendering this biosynthetic pathway an attractive target for antiparasitic drug design. The recombinant human adenine phosphoribosyltransferase (hAPRT) structure was resolved in the presence of AMP in the active site to 1.76 A resolution and with the substrates PRPP and adenine simultaneously bound to the catalytic site to 1.83 A resolution. An additional structure was solved containing one subunit of the dimer in the apo-form to 2.10 A resolution. Comparisons of these three hAPRT structures with other 'type I' PRTases revealed several important features of this class of enzymes. Our data indicate that the flexible loop structure adopts an open conformation before and after binding of both substrates adenine and PRPP. Comparative analyses presented here provide structural evidence to propose the role of Glu104 as the residue that abstracts the proton of adenine N9 atom before its nucleophilic attack on the PRPP anomeric carbon. This work leads to new insights to the understanding of the APRT catalytic mechanism.
Structural Complexes of Human Adenine Phosphoribosyltransferase Reveal Novel Features of the APRT Catalytic Mechanism.,Silva CH, Silva M, Iulek J, Thiemann OH J Biomol Struct Dyn. 2008 Jun;25(6):589-98. PMID:18399692
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.