Acetyltransferase with p-aminobenzoic acid (PABA) as substrate was investigated in the cytosolic fraction of the placenta, liver, adrenals, lungs, kidneys, intestine from human fetuses and the liver, lungs, kidneys and intestinal mucosa from adult subjects. All tissue specimens assayed catalyzed the acetylation of PABA at a significant rate. The activity (expressed as nmol of product formed/min/mg protein; mean ± SE) was 1.10 ± 0.59 in the fetal liver, 0.66 ± 0.04 in the placental and 3.87 ± 0.53 in the adult liver cytosol. Among the fetal tissues, the adrenals had the highest (2.36 ± 0.78) and the gut the lowest activity (0.71 ± 0.11). The acetyltransferase activity (mean ± SE) in the lungs, kidneys and intestinal mucosa from adult subjects was 1.19 ± 0.15; 1.34 ± 0.04 and 3.80 ± 0.34, respectively.
Sulfotransferase with 2-naphthol as substrate was investigated in the cytosolic fraction of human fetal liver, lungs, kidneys, adrenal glands, intestine and placenta and also in liver, lungs, kidneys, intestinal and urinary bladder mucosa from human adult subjects. All tissue specimens assayed catalyzed the sulfation of 2-naphthol at a significant rate. The activity (expressed as pmole per minute per milligram protein; mean ± SD) was 211 ± 197 (n = 46) fetal liver; 22 ± 12 (n = 29) placenta; 625 ± 205 (n = 42) human adult liver. In fetal kidneys (576 ± 177; n = 6) and gut (558 ± 293; n = 6) the activity was twice as high as in liver. In the lungs (273 ± 125; n = 6) and in the adrenals (174 ± 119; n = 19) the sulfotransferase activity was comparable with the hepatic one. In human adult extrahepatic tissues the highest activity was found in the intestinal mucosa (153 ± 49; n = 4) and the lowest one in the urinary bladder mucosa (16 ± 4; n = 4). This paper shows that the sulfotransferase has a wide distribution in the human fetus and the distribution pattern of this enzyme is different in the human fetus and adult subject.
Glutathione S-transferase (GST) was investigated with benzo(a)pyrene-4,5-oxide (BPO) as substrate in tissue specimens from 26 fetal and 27 adult livers and 27 placentas. The average (+/- SEM) of GST activity in the cytosol was 1.80 +/- 0.18 (fetal liver), 3.05 +/- 0.30 (adult liver) and 1.18 +/- 0.07 (placenta) nmol/min/mg. GST was also investigated in human fetal and adult lungs, kidneys and gut. In these tissues the average (+/- SEM) GST activity ranged between 0.71 +/- 0.12 (adult intestine) and 2.11 +/- 0.18 (fetal lungs) nmol/min/mg. Whereas in the fetal liver the conjugation of BPO was catalyzed at a rate of about two-thirds of the adult rate, similar or higher GST activities were found in the fetal non-hepatic tissues as compared to the adult organs. No correlation was found between the activity of the GST in fetal liver and placenta and the gestational age (11-25 weeks). GST develops before the 11th week of gestation and it does not undergo changes during the mid-gestation. No correlation was found between GST activity in adult liver and age (32-70 years).
The epoxide hydrolase and glutathione S-transferase activity towards styrene oxide as substrate were investigated and compared in fetal and adult human liver cytosols. The rate of formation of styrene glycol from styrene oxide (nmole/min/mg protein) was 0.23 +/- 0.02 (means +/- SE; n = 10) in fetal and 0.83 +/- 0.05 (means +/- SE; n = 14) in adult liver specimens. The enzyme followed Michealis-Menten kinetics in the fetal liver. In adult liver specimens the enzyme showed biphasic kinetics. For comparative purposes, the cytosolic glutathione S-transferase activity was investigated in the cytosolic fractions from the same liver specimens. The fetal activity was 40% of the adult activity 3.9 +/- 0.50 (means +/- SE; n = 10) versus 9.94 +/- 1.75 (means +/- SE; n = 14) nmoles/min/mg protein.
The epoxide hydrolase activity with styrene oxide as substrate was investigated in the nuclear fraction of human fetal and adult liver specimens. All investigated liver fractions catalyzed the hydration of styrene oxide and the average epoxide hydrolase activities were 0.37 and 1.90 nmol/min/mg protein in fetal and adult specimens, respectively. The enzyme followed Michaelis-Menten kinetics in fetal nuclear fraction and biphasic kinetics in adult livers. The nuclear/microsomal enzyme activity ratios of epoxide hydrolase were 0.09 and 0.11 for fetal and adult livers, respectively.
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