2-(14)C-orotic acid | 10491-81-3

• 分子结构分类: 有机化合物 - 有机杂环化合物 - 唑类
• 英文名称: 2-(14)C-orotic acid
• 英文别名: 2,6-dioxo-1,2,3,6-tetrahydro-pyrimidine-4-carboxylic acid；(2-¹⁴C)-Orotsaeure；2,4-dioxo-(214C)1H-pyrimidine-6-carboxylic acid
• CAS: 10491-81-3
• 化学式: C₅H₄N₂O₄
• 分子量: 158.087
• InChiKey: PXQPEWDEAKTCGB-RHRFEJLCSA-N

物化性质

• 熔点：
  343-345 °C (decomp)

计算性质

• 辛醇/水分配系数(LogP)：
  -1.4
• 重原子数：
  11
• 可旋转键数：
  1
• 环数：
  1.0
• sp3杂化的碳原子比例：
  0.0
• 拓扑面积：
  95.5
• 氢给体数：
  3
• 氢受体数：
  4

反应信息

• 作为反应物：
  描述：

  2-(14)C-orotic acid 、 磷酸核糖焦磷酸 在 Salmonella typhimurium OMP synthase wild type 作用下， 生成 2-(14)C-OMP
  参考文献：
  名称：

  Loop Residues and Catalysis in OMP Synthase

  摘要：

  Residue-to-alanine mutations and a two-amino acid deletion have been made in the highly conserved catalytic loop (residues 100-109) of Salmonella typhimurium OMP synthase (orotate phosphoribosyltransferase, EC 2.4.2.10). As described previously, the K103A mutant enzyme exhibited a 10(4)-fold decrease in k(cat)/K-M for PRPP; the K100A enzyme suffered a 50-fold decrease. Alanine mutations at His105 and Glu107 produced 40- and 7-fold decreases in k(cat)/K-M, respectively, and E101A, D104A, and G106A were slightly faster than the wild-type (WT) in terms of k(cat), with minor effects on k(cat)/K-M. Equilibrium binding of OMP or PRPP in binary complexes was affected little by loop mutation, suggesting that the energetics of ground-state binding have little contribution from the catalytic loop, or that a favorable binding energy is offset by costs of loop reorganization. Pre-steady-state kinetics for mutants showed that K103A and E107A had lost the burst of product formation in each direction that indicated rapid on-enzyme chemistry for WT, but that the burst was retained by H105A. Delta 102 Delta 106, a loop-shortened enzyme with Ala102 and Gly106 deleted, showed a 10(4)-fold reduction of k(cat) but almost unaltered K-D values for all four substrate molecules. The 20% (i.e., 1.20) intrinsic [1'-H-3]OMP kinetic isotope effect (KIE) for WT is masked because of high forward and reverse commitment factors. K103A failed to express intrinsic KIEs fully (1.095 +/- 0.013). In contrast, H105A, which has a smaller catalytic lesion, gave a [1'-3H]OMP KIE of 1.21 +/- 0.0005, and E107A (1.179 +/- 0.0049) also gave high values. These results are interpreted in the context of the X-ray structure of the complete substrate complex for the enzyme [Grubmeyer, C., Hansen, M. R., Fedorov, A. A., and Almo, S. C. (2012) Biochemistry 51 (preceding paper in this issue, DOI 10.1021/bi300083p)]. The full expression of KIEs by H105A and E107A may result from a less secure closure of the catalytic loop. The lower level of expression of the KIE by K103A suggests that in these mutant proteins the major barrier to catalysis is successful closure of the catalytic loop, which when closed, produces rapid and reversible catalysis.

  DOI：

  10.1021/bi300082s