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Perinatal developmental changes in hepatic UDP-glucuronyltransferase.
The Biochemical Journal
|March 15, 1980
Summary
Rat liver UDP-glucuronyltransferase matures postnatally, showing increased regulation and altered substrate affinity. Enzyme activity is similar in newborns and adults at saturating conditions, indicating developmental changes in enzyme properties.
Area of Science:
- Biochemistry
- Developmental Biology
- Pharmacology
Background:
- UDP-glucuronyltransferase (UGT) is crucial for drug and xenobiotic metabolism.
- Postnatal development involves significant changes in hepatic enzyme activity.
- Previous studies indicated a decline in UGT activity after birth.
Purpose of the Study:
- To investigate postnatal developmental changes in rat hepatic microsomal UDP-glucuronyltransferase.
- To characterize kinetic and regulatory differences in UGT between newborn and adult rats.
Main Methods:
- Kinetic analysis of UDP-glucuronyltransferase activity using p-nitrophenol as a substrate.
- Assessment of enzyme response to varying UDP-glucuronic acid concentrations.
- Evaluation of allosteric regulation by UDP-N-acetylglucosamine.
- Investigation of enzyme sensitivity to membrane lipid perturbation (detergent, phospholipase A).
Main Results:
- The postnatal decline in UGT activity is substrate concentration-dependent.
- Newborn UGT exhibits higher affinity for UDP-glucuronic acid but similar Vmax compared to adult UGT.
- Adult UGT is allosterically activated by UDP-N-acetylglucosamine, unlike newborn UGT.
- Differential responses to membrane perturbation suggest changes in enzyme-lipid interactions.
Conclusions:
- Rat hepatic UGT matures postnatally, developing enhanced allosteric regulation rather than changes in active site number.
- Developmental changes involve alterations in substrate affinity and regulatory properties.
- These maturational changes impact the enzyme's interaction with its membrane environment and its overall metabolic capacity.