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Pyruvate carboxylase activity in chorionic villi: possibility of application to prenatal diagnosis
V Barash1, S Khassis, M Granat
1Department of Clinical Biochemistry, Hadassah University Hospital, Jerusalem, Israel.
Insights
Pyruvate carboxylase (PC) activity in chorionic villi samples (CVS) during early pregnancy was analyzed. The enzyme showed properties similar to liver PC and significantly higher activity than in amniotic fluid fibroblasts.
Area of Science:
- Biochemistry
- Human Embryology
- Enzymology
Background:
- Pyruvate carboxylase (PC) is a key mitochondrial enzyme involved in anaplerosis.
- Understanding PC activity in early human development is crucial for metabolic studies.
Purpose of the Study:
- To characterize pyruvate carboxylase (PC) activity and kinetics in chorionic villi samples (CVS) during early gestation.
- To compare PC activity in CVS with other fetal tissues.
Main Methods:
- Enzyme kinetic assays were performed on 27 chorionic villi samples (CVS) from 9-12 weeks of gestation.
- PC activity was localized to the mitochondrial fraction.
- Kinetic parameters (Km, optimal pH) were determined.
Main Results:
- PC activity in CVS was found to be 3.2 +/- 0.3 nmol/min/mg protein.
- The kinetic properties of CVS PC were similar to those of liver PC.
- Over 75% of PC activity was recovered in the mitochondrial fraction.
Conclusions:
- Pyruvate carboxylase is active in early human pregnancy (CVS).
- The enzyme exhibits kinetic properties comparable to its liver counterpart.
- PC activity in CVS is substantially higher than in amniotic fluid fibroblasts, suggesting tissue-specific roles.
Abstract:
Pyruvate carboxylase (PC) activity was assayed in 27 chorionic villi samples (CVS) obtained at 9-12 weeks of gestation. The kinetic properties of the CVS enzyme were similar to those of liver PC; more than 75% of PC activity was recovered in the mitochondrial fraction of CVS. Apparent Km for pyruvate, ATP, acetyl CoA and HCO3- in the presence of saturation concentrations of the other reactants, were 0.3, 0.44, 0.015 and 6.0 mmol/l, respectively. The optimum pH was 7.5-8.0. The activity of PC in CVS was 3.2 +/- 0.3 nmol/min/mg protein, which is severalfold higher than that of amniotic fluid fibroblasts.