Phosphorylation inactivates Escherichia coli isocitrate dehydrogenase by preventing isocitrate binding

A. M. Dean, M. H I Lee, D. E. Koshland

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Equilibrium binding studies demonstrate that purified Escherichia coli isocitrate dehydrogenase binds isocitrate, α-ketoglutarate, NADP, and NADPH at 1:1 ratios of substrate to enzyme monomer. The phosphorylated enzyme, which is completely inactive, is unable to bind isocitrate but retains the ability to bind NADP and NADPH. Replacement of serine 113, which is the site of phosphorylation, by aspartate results in an inactive enzyme that is unable to bind isocitrate. Replacement of the same serine with other amino acids (lysine, threonine, cysteine, tyrosine, and alanine) produces active enzymes that bind both substrates. Hence, the negative charge of an aspartate or a phosphorylated serine at site 113 inactivates the enzyme by preventing the binding of isocitrate.

Original languageEnglish (US)
Pages (from-to)20482-20486
Number of pages5
JournalJournal of Biological Chemistry
Volume264
Issue number34
StatePublished - 1989

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