Inactivation of liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase by o-phthalaldehyde.
The two activities of chicken liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase were inactivated by o-phthalaldehyde. Absorbance and fluorescence spectra of the modified enzyme were consistent with the formation of an isoindole derivative (1 mol/mol of enzyme subunit). The inactivation of 6-phosphofructo-2-kinase by o-phthalaldehyde was faster than the inactivation of fructose-2,6-bisphosphatase, which was concomitant with the increase in fluorescence. The substrates of 6-phosphofructo-2-kinase did not protect the kinase against inactivation, whereas fructose-2,6-bisphosphate fully protected against o-phthalaldehyde-induced inactivation of the bisphosphatase. Addition of dithiothreitol prevented both the increase in fluorescence and the inactivation of fructose-2,6-bisphosphatase, but not that of 6-phosphofructo-2-kinase. It is proposed that o-phthalaldehyde forms two different inhibitory adducts: a non-fluorescent adduct in the kinase domain and a fluorescent isoindole derivative in the bisphosphatase domain. A lysine and a cysteine residue could be involved in fructose-2,6-bisphosphate binding in the bisphosphatase domain of the protein.
Rider
M H
MH
Hormone and Metabolic Research Unit, University of Louvain Medical School, Brussels, Belgium.
Hue
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D000447:Aldehydes / Q000494:pharmacology*; D000818:Animals; D002645:Chickens; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008099:Liver / Q000201:enzymology*; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors*; D010770:Phosphotransferases / Q000037:antagonists & inhibitors*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D009764:o-Phthalaldehyde / Q000494:pharmacology*
D000447:Aldehydes; D009764:o-Phthalaldehyde; D010770:Phosphotransferases; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases; D004229:Dithiothreitol