TY - JOUR
T1 - Nuclear metabolism. II. Further studies on epoxide hydrolase activity
AU - Gazzotti, Giuliano
AU - Garattini, Enrico
AU - Salmona, Mario
PY - 1981
Y1 - 1981
N2 - Apparent Km- and Vmax-values of nuclear styrene 7,8-oxide hydrolase were determined at different protein concentrations. In the protein concentrations range used no significant differences in the apparent Km-values were observed. The influence of the incubation with different modifiers (i.e. SKF-525A, metyrapone, 1,2-epoxy-3,3,3 trichloropropane, cyclohexene oxide) at two different concentrations on this enzyme activity was also determined. Cyclohexene oxide and 1,2-epoxy-3,3,3-trichloropropane, two well known inhibitors of the microsomal epoxide hydrolase(s) caused a marked inhibition, metyrapone had a strong activating effect whereas SKF-525A had no effect. In vivo pretreatment with phenobarbital significantly induced the nuclear epoxide hydrolase whereas β-naphthoflavone caused a lower degree of induction. This pattern is quantitatively different but qualitatively very similar to the microsomal one. Moreover a toxifying to detoxifying enzymatic activity balance is attempted for the metabolization of the alkenic double bond of styrene, taking into account the ratio between the styrene monooxygenase (toxifying enzyme) and the styrene 7,8-oxide hydrolase (detoxifying enzyme) after the above mentioned pretreatments, both in the microsomal and nuclear fractions.
AB - Apparent Km- and Vmax-values of nuclear styrene 7,8-oxide hydrolase were determined at different protein concentrations. In the protein concentrations range used no significant differences in the apparent Km-values were observed. The influence of the incubation with different modifiers (i.e. SKF-525A, metyrapone, 1,2-epoxy-3,3,3 trichloropropane, cyclohexene oxide) at two different concentrations on this enzyme activity was also determined. Cyclohexene oxide and 1,2-epoxy-3,3,3-trichloropropane, two well known inhibitors of the microsomal epoxide hydrolase(s) caused a marked inhibition, metyrapone had a strong activating effect whereas SKF-525A had no effect. In vivo pretreatment with phenobarbital significantly induced the nuclear epoxide hydrolase whereas β-naphthoflavone caused a lower degree of induction. This pattern is quantitatively different but qualitatively very similar to the microsomal one. Moreover a toxifying to detoxifying enzymatic activity balance is attempted for the metabolization of the alkenic double bond of styrene, taking into account the ratio between the styrene monooxygenase (toxifying enzyme) and the styrene 7,8-oxide hydrolase (detoxifying enzyme) after the above mentioned pretreatments, both in the microsomal and nuclear fractions.
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U2 - 10.1016/0009-2797(81)90006-5
DO - 10.1016/0009-2797(81)90006-5
M3 - Article
C2 - 7226277
AN - SCOPUS:0019419922
VL - 35
SP - 311
EP - 318
JO - Chemico-Biological Interactions
JF - Chemico-Biological Interactions
SN - 0009-2797
IS - 3
ER -