TY - JOUR T1 - Theoretical studies of the quinolinic acid to nicotinic acid mononucleotide transformation. AU - Rozenberg,Aleksandr, AU - Lee,Jeehiun K, PY - 2008/10/29/pubmed PY - 2010/10/5/medline PY - 2008/10/29/entrez SP - 9314 EP - 9 JF - The Journal of organic chemistry JO - J Org Chem VL - 73 IS - 23 N2 - Quinolinate phosphoribosyl transferase (QPRTase) is an essential enzyme that catalyzes the transformation of quinolinic acid (QA) to nicotinic acid mononucleotide (NAMN), a key step on the de novo pathway for nicotinamide adenine dinucleotide (NAD) biosynthesis. We describe herein a theoretical study of the intrinsic energetics associated with the possible mechanistic pathways by which QA forms NAMN. Our main interest is in probing the decarboxylation step, which is intriguing since the product is a vinylic anion, not unlike the reaction catalyzed by orotidine 5'-monophosphate (OMP) decarboxylase, an enzyme whose mechanism is under fierce debate. Our calculations indicate that a path involving a quinolinic acid mononucleotide (QAMN) intermediate is the most energetically attractive, favoring decarboxylation. We also find that the monocarboxylate form of QAMN will decarboxylate much more favorably energetically than will the dicarboxylate form of QAMN. Furthermore, our calculations indicate that decarboxylation is not a likely first step; the substrate in such a mechanism would prefer to decarboxylate at the C3 position, not the desired C2 position. We also discuss our results in the context of existing experimental data. SN - 1520-6904 UR - https://www.unboundmedicine.com/medline/citation/18954112/Theoretical_studies_of_the_quinolinic_acid_to_nicotinic_acid_mononucleotide_transformation_ L2 - https://doi.org/10.1021/jo8012379 DB - PRIME DP - Unbound Medicine ER -