text: A novel variant L263F in human inosine 5'-monophosphate dehydrogenase 2 is associated with diminished enzyme activity.
  BACKGROUND AND OBJECTIVE: Inosine 5'-monophosphate dehydrogenase 2 is required for purine synthesis in activated lymphocytes. Variants in the IMPDH2 gene may account for the large inter-individual variability in baseline enzyme activity, immunosuppressive efficacy and side effects in transplant recipients receiving mycophenolic acid. Therefore, the objective of this study was to identify and functionally characterize IMPDH2 variants. METHODS: DNA samples from 152 solid organ transplant patients were screened at exons and exon/intron junctions of the IMPDH2 genes by PCR amplification followed by bidirectional direct DNA sequencing. Genetic variant was constructed by site-directed mutagenesis and transformed to an inosine 5'-monophosphate dehydrogenase-deficient strain of Escherichia coli h712. Proteins were purified to homogeneity and the enzymatic activity was measured by reduced nicotinamide adenine dinucleotide production. RESULTS: Nine genetic variants were identified in the IMPDH2 gene, with frequencies of the rarer alleles ranging from 0.5 to 10.2%. A novel nonsynonymous variant L263F was identified, and the kinetic assay demonstrated that the inosine 5'-monophosphate dehydrogenase activity of L263F variant was decreased to 10% of the wild-type. The Ki for mycophenolic acid inhibition of the L263F variant was comparable with the wild-type, and the variant Km for inosine 5'-monophosphate and nicotinamide adenine dinucleotide did not change significantly. CONCLUSIONS: IMPDH2 has low genetic diversity, but the nonsynonymous variant L263F has a significant impact on inosine 5'-monophosphate dehydrogenase activity. This novel functional variant may be one of the factors contributing to the inter-individual difference of baseline inosine 5'-monophosphate dehydrogenase activity as well as drug efficacy and adverse events in transplant patients.
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entities.type: CHEMICAL CHEMICAL GENE-N GENE-N GENE-N GENE-N GENE-Y GENE-Y GENE-N GENE-N CHEMICAL GENE-N GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y GENE-N GENE-Y CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL
entities.text: nicotinamide adenine dinucleotide inosine 5'-monophosphate L263F inosine 5'-monophosphate dehydrogenase L263F L263F IMPDH2 IMPDH2 L263F inosine 5'-monophosphate dehydrogenase inosine 5'-monophosphate inosine 5'-monophosphate dehydrogenase Inosine 5'-monophosphate dehydrogenase 2 IMPDH2 IMPDH2 inosine 5'-monophosphate dehydrogenase IMPDH2 L263F human inosine 5'-monophosphate dehydrogenase 2 mycophenolic acid inosine 5'-monophosphate nicotinamide adenine dinucleotide inosine 5'-monophosphate inosine 5'-monophosphate Inosine 5'-monophosphate mycophenolic acid inosine 5'-monophosphate