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Jejunal brush-border folate hydrolase. A novel enzyme
1Department of Internal Medicine, University of California, Davis, School of Medicine 95616.
The Western Journal of Medicine
|December 1, 1991
Summary
Jejunal brush-border folate hydrolase is crucial for absorbing dietary folate (vitamin B9). Its activity is inhibited in conditions causing folate deficiency, highlighting its importance in nutrient absorption.
Area of Science:
- Biochemistry
- Gastroenterology
- Nutritional Science
Background:
- Dietary folate, essential for DNA synthesis and cell regeneration, exists as pteroylpolyglutamates.
- Intestinal absorption involves hydrolysis of pteroylpolyglutamates to pteroylglutamate.
- Jejunal brush-border folate hydrolase has been identified as essential and rate-limiting in folate absorption.
Purpose of the Study:
- To investigate the role and characteristics of jejunal brush-border folate hydrolase in folate absorption.
- To understand the inhibition of folate absorption in various disease states.
Main Methods:
- Enzyme activity assays to assess brush-border folate hydrolase function.
- Immunoprecipitation using specific antibodies to characterize the enzyme's molecular weight.
- Analysis of folate absorption mechanisms in relation to enzyme activity.
Main Results:
- Jejunal brush-border folate hydrolase activity is inhibited in conditions like celiac sprue, tropical sprue, and chronic alcoholism.
- The enzyme is an exopeptidase located on the jejunal brush-border surface.
- In pigs, the enzyme has a molecular weight of 240 kd, likely a homodimer of a 120-kd protein.
Conclusions:
- Jejunal brush-border folate hydrolase is vital for dietary folate absorption.
- Dysregulation of this enzyme contributes to folate deficiency in various clinical conditions.
- Controlling the synthesis and expression of brush-border folate hydrolase may be key to managing folate availability.