Affirmation of a general base of Hafnia alvei Aspartase by Organic Solvent Perturbation Method
نویسنده
چکیده
cept on the vertical axis is 95. From the data plotted in accordance with equation 1, the values found for the dissociation constant Ki and the inactivation rate constant kinact were 38 ± 4 × 10 M and 1.05 ± 0.08 × 10 sec, respectively. These values compare very favorably with those for mechanismbased inhibitors of phosphatases. As shown in Figure 4, menadione shares critical structural features with phosphotyrosine. Therefore, menadione might have the favorable dissociation constant. For example, incubation of cdc25 phosphatase with 1,4-benzoquinone did not show inhibition, suggesting that the aromatic ring of inactivator is necessary for its action. In conclusion, the active site of cdc25A phosphatase could be irreversibly inactivated by menadione. We have also been able to provide data, Ki and kinact, that show the efficiency of inactivation. Based on these data, modifying the inactivator is matter of future interest. Acknowledgment. We thank Dr. David Beach of the Cold Spring Harbor Laboratory for kindly providing the Figure 4. Structural similarity of phosphotyrosine and menadione. O P O Try O O
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Binding Properties of an Allosteric Activator Site of Aspartase from Hafnia alvei
Aspartase is a textbook example of a highly specific enzyme with no identifiable alternative substrates. The enzyme is specific to aspartate and fumarate, but NH2OH can be substituted for ammonia as a substrate. A variety of divalent metal ions a such as Mg, Mn, Zn and Co activate the reaction. Initial velocity data for the aspartase from Hafnia alvei are consistent with rapid equilibrium order...
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