Rabbit lung flavin-containing monooxygenase. Purification, characterization, and induction during pregnancy

Area of Science:

• Biochemistry
• Enzymology
• Pharmacology

Background:

• Flavin-containing monooxygenases (FMOs) are crucial enzymes involved in the metabolism of xenobiotics and endogenous compounds.
• While FMOs are well-characterized in some species, their specific forms and roles during physiological states like pregnancy are less understood.

Purpose of the Study:

• To purify and characterize a flavin-containing monooxygenase (FMO) from pregnant rabbit lung microsomes.
• To investigate the changes in FMO activity and quantity during gestation.
• To determine if the lung FMO is distinct from other known FMO forms.

Main Methods:

• Purification of FMO from rabbit lung microsomes using standard biochemical techniques.
• Characterization of enzyme kinetics, substrate specificity, and physical properties (molecular weight, cofactor content).
• Immunoquantitation using antibodies to measure enzyme levels throughout gestation; Western blotting to compare with liver FMO.

Main Results:

• A flavin-containing monooxygenase (FMO) with an apparent molecular weight of 59,000 was purified.
• The rabbit lung FMO exhibited distinct properties from the pig liver enzyme, including a broader pH optimum and resistance to cholate inhibition.
• Enzyme activity and amount increased up to 5-fold by the 28th day of gestation, with no detectable lung-form FMO in liver microsomes.

Conclusions:

• Rabbit lung flavin-containing monooxygenase (FMO) is a distinct enzyme form.
• This FMO is significantly induced during late pregnancy in rabbits.
• The physiological role of this pregnancy-induced lung FMO remains to be elucidated.