Modification of the kinetics and regulatory properties of bovine hepatic fructose 1,6-diphosphatase with pyridoxal 5'-phosphate |
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Authors: | C J Marcus W L Byrne A M Geller |
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Institution: | 1. Departments of Biochemistry Duke University Durham, North Carolina 27706, USA;2. The University of Tennessee Medical Units Memphis, Tennessee 38163, USA |
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Abstract: | Treatment of purified fructose 1,6-diphosphatase from bovine liver (which is maximally active at neutral pH) with pyridoxal 5'-phosphate produces changes in the spectral, catalytic, and allosteric properties of the enzyme. After modification the Michaelis constants for fructose-1,6-diphosphate and Mg2+ are increased, and inhibition by AMP is decreased. Substrate inhibition is decreased, but not abolished; the curve is merely shifted toward higher substrate concentration. Fructose-1, 6-diphosphate protects against the increases in the Km for fructose-1, 6-diphosphate and the Km for Mg2+, and against the changes in substrate inhibition, but not against the changes in AMP inhibition. AMP protects against the changes in AMP inhibition and the increase in the Km for magnesium, but does not prevent the changes in substrate inhibition or the increase in the Km for fructose-1, 6-diphosphate. The pH curves in the modified enzyme are altered at high, but not at low, substrate concentration. |
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