Orotic acid (OA) is an intermediate in de novo pyrimidine biosynthesis that may be used to study the specificity and kinetics of orotate phosphoribosyltransferase (OPRT) which catalyzes the reversible phosphoribosyl transfer from 5′-phospho-α-d-ribose 1′-diphosphate (PRPP) to orotic acid (OA), forming pyrophosphate and orotidine 5′-monophosphate (OMP). Orotic acid is used as a starting material for the potential commercial bioproduction of uridine 5′-monophosphate (UMP) by microbes such as Corynebacterium ammoniagenes (ATCC 6872) or Saccharomyces cerevisiae. OA may be used to study the AMPK/SREBP-1 dependent cell signaling pathway and transcription regulation mechanisms that induce hepatic lipogenesis.