A two-stage assay was used to study the effect of organic solvents on the activation of and the catalysis by chloroplast fructose-1,6-bisphosphatase. Irrespective of chemical structure, all the organic solvents tested had a dual effect on the enzyme. In the activation they stimulated and inhibited at low and high concentrations, respectively, in a process that required dithiohreitol, fructose-1,6-bisphosphate, and Ca2+. Conversely, organic solvents inhibited catalysis. The enhancement in fructose-1,6-bisphosphatase activity did not arise from a change in the molecular weight of the enzyme and correlated positively with the hydrophobic character of the organic solvent. In the presence of 2-propranol, all the activation constants for modulators (fructose-1,6-bisphosphate, Ca2+, thioredoxin-f) were lower than in a strictly aqueous medium. Monothiols were also functional in the activation of chloroplast fructose-1,6-bisphosphatase, although they were less effective than dithiols. Sulfhydryl compounds decreased the concentration of fructose-1,6-bisphosphate required for the activation of the enzyme, and 2-propanol lowered this requirement further. Arrhenius plots were nonlinear for the enzyme activation and linear for the hydrolytic step. The anomalous temperature dependence of the chloroplast fructose-1,6-bisphosphatase activation was indicative of a cooperative process. The data obtained in this study indicate that the concerted activation of chloroplast fructose-1,6-bisphosphatase is favored in a medium less polar than water.
Documento: | Artículo |
Título: | The effect of organic solvents on the activation and the activity of spinach chloroplast fructose-1,6-bisphosphatase |
Autor: | Corley, E.; Wolosiuk, R.A. |
Filiación: | Instituto de Investigaciones Bioquimicas, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina |
Palabras clave: | enzyme; fructose bisphosphatase; organic solvent; chloroplast; higher plant; nonhuman; priority journal; 1-Propanol; Calcium; Chloroplasts; Dithiothreitol; Enzyme Activation; Fructose-Bisphosphatase; Fructosediphosphates; Plant Proteins; Solvents; Support, Non-U.S. Gov't; Temperature |
Año: | 1985 |
Volumen: | 260 |
Número: | 7 |
Página de inicio: | 3978 |
Página de fin: | 3983 |
Título revista: | Journal of Biological Chemistry |
Título revista abreviado: | J. BIOL. CHEM. |
ISSN: | 00219258 |
CODEN: | JBCHA |
CAS: | fructose bisphosphatase, 9001-52-9; 1-Propanol, 71-23-8; Calcium, 7440-70-2; Dithiothreitol, 3483-12-3; fructose-1,6-diphosphate, 488-69-7; Fructose-Bisphosphatase, EC 3.1.3.11; Fructosediphosphates; Plant Proteins; Solvents; thioredoxin f |
Registro: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00219258_v260_n7_p3978_Corley |