The reactive cysteine residue of pig kidney fructose 1,6-bisphosphatase is related to a fructose 2,6-bisphosphate allosteric site |
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Authors: | A Reyes E Hubert J C Slebe |
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Institution: | Instituto de Bioquimica, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile |
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Abstract: | Modification of a highly reactive cysteine residue of pig kidney fructose 1,6-bisphosphatase with N-ethylmaleimide results in the loss of activation of the enzyme by monovalent cations. Low concentrations of fructose 2,6-bisphosphate or high (inhibitory) levels of fructose 1,6-bisphosphate protect the enzyme against the loss of monovalent cation activation, while non-inhibitory concentrations of the substrate gave partial protection. The allosteric inhibitor AMP markedly increases the reactivity of the cysteine residue. The results indicate that fructose 2,6-bisphosphate can protect the enzyme against the loss of potassium activation by binding to an allosteric site. High levels of fructose 1,6-bisphosphate probably inhibit the enzyme by binding to this allosteric site. |
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