EC Number   |
General Information |
Reference |
|---|
   1.13.11.91 | metabolism |
active-site cluster models and comparison of CDO, EC 1.13.11.20, and 3-mercaptopropionate dioxygenase MDO. The enzymes have different iron(III)-superoxo-bound structures due to differences in ligand coordination. The differences in the second-coordination sphere and particularly the position of a positively charged Arg residue result in changes in substrate positioning, mobility and enzymatic turnover. For both enzymes, the second oxygen atom transfer has the highest barriers with magnitudes of 14.2 and 15.8 kcal/mol, respectively. Both enzymes have an open-shell singlet-spin iron(III)-superoxo reactant with the substrate bound as a bidentate ligand in the equatorial plane, in MDO the quintet spin state is within 1 kcal/mol. MDO binds the substrate through two anionic bonds of the substrate carboxylate and thiolate groups, and a strong hydrogen-bonding interaction of a Tyr residue towards the superoxo group in MDO is found |
-, 764498 |
| 1.13.11.91 | physiological function |
a network of hydrogen bonds connects residues H157-Y159 and Fe-bound ligands within the enzymatic Fe site. The hydroxyl group of Y159 hydrogen bonds to Fe-bound NO and, by extension, Fe-bound oxygen during native catalysis. This interaction alters both the NO binding affinity and rhombicity of the 3-mercaptopropanoate-bound iron-nitrosyl site |
758826 |
| 1.13.11.91 | physiological function |
mutants are impaired in growth on 3,3-thiodipropionic acid |
759466 |
| 1.13.11.91 | physiological function |
the monoprotonated ES complexes with 3-mercaptopropionic acid and cysteine have different pKs. At higher pH, kcat decreases sigmoidally with a similar pK regardless of substrate. Loss of reactivity at high pH is attributed to deprotonation of tyrosine 159 and its influence on dioxygen binding. A mechanism model shows deprotonation of tyrosine 159 both blocks oxygen binding and concomitantly promotes cystine formation |
-, 758787 |
| 1.13.11.91 | physiological function |
the pL-dependent activity of MDO can be rationalized assuming a diprotic enzyme model in which three ionic forms of the enzyme are present [cationic, E(z+1), neutral, Ez, and anionic, E(z-1)]. The activities observed for substrates 3-mercaptopropanoate and cysteine appear to be dominated by electrostatic interactions within the enzymatic active site |
758696 |
