Further evidence for an essential histidyl residue at the active site of pig liver 5-aminolevulinic acid dehydratase

Photoxidation with methylene blue and rose bengal and chemical modification by diethylpyrocarbonate of pig liver 5-aminolevulinic acid dehydratase produced strong inactivation of the enzyme which was concentration dependent. Loss of enzyme activity by both photoxidation and ethoxyformylation was pH...

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Detalles Bibliográficos
Autores principales: Fukuda, H., Dopera De Kracoff, Y.E., Inigo, L.E., Paredes, S.R., Ferramola De Sancovich, A.M., Sancovich, H.A., Batlle, A.M.C.
Formato: JOUR
Materias:
5-Aminolevulinic acid dehydratase
Diethylpyrocarbonate
Histidyl residues
Methylene blue
Rose Bengal
diethyl pyrocarbonate
histidine
methylene blue
porphobilinogen synthase
rose bengal
animal cell
article
enzyme active site
enzyme modification
nonhuman
photooxidation
swine
Animal
Binding Sites
Enzyme Inhibitors
Histidine
Hydrogen-Ion Concentration
Kinetics
Liver
Macromolecular Systems
Methylene Blue
Photochemistry
Porphobilinogen Synthase
Support, Non-U.S. Gov't
Swine
Animalia
Sus scrofa
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_14756366_v3_n4_p295_Fukuda
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
Descripción
Sumario:Photoxidation with methylene blue and rose bengal and chemical modification by diethylpyrocarbonate of pig liver 5-aminolevulinic acid dehydratase produced strong inactivation of the enzyme which was concentration dependent. Loss of enzyme activity by both photoxidation and ethoxyformylation was pH and time-dependent and protected by the presence of the substate and competitive inhibitors. The rate of inactivation was directly related to the state of protonation of histidyl groups, the unprotonated from being modified at a much faster rate than the protonated form. Plots of the pseudo-first order rate constants for 5-aminolevulinic acid dehydratase inactivation against pH resulted in typical titration curves showing inflection points at about pH 6.4 for methylene blue and rose bengal and 6.8 for diethylpyrocarbonate providing further and unequivocal evidence for the existence of critical histidyl groups at the active centre of the enzyme. © 1990 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.

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