XGPRT - Mycophenolic Acid Resistance - The bacterial enzyme XGPRT (xanthine-guanine phosphoribosyl transferase) is analogous to the mammalian enzyme HGPRT (hypoxanthine-guanine phosphoribosyl transferase). Both XGPRT and HGPRT are enzymes of the salvage pathway.

Normal mammalian cells are sensitive to mycophenolic acid because it inhibits HGPRT-catalyzed conversion of IMP to XMP; this sensitivity is greatly enhanced by the presence of aminopterin, which blocks endogenous purine biosynthesis.The bacterial XPGRT gene serves as a dominant selectable marker on a culture medium containing mycophenolic acid, adenine and xanthine.