Functional specificity of jejunal brush-border pteroylpolyglutamate hydrolase in pig

ArticleinThe American journal of physiology 260(6 Pt 1):G865-72 · July 1991with7 Reads
Source: PubMed
To determine the functional specificity of intestinal brush-border pteroylpolyglutamate hydrolase (PPH), we compared the regional location of in vivo hydrolysis of pteroyltriglutamate (PteGlu3) with the location of activity and immunoreactivity of the enzyme in the pig. After in vivo incubations, PteGlu3 hydrolytic products were recovered from intestinal segments in the jejunum but not from the ileum. Brush-border PPH activity in fractionated mucosa was 10-fold greater in the jejunum than in the ileum, whereas the activity of intracellular PPH was increased in the distal ileum. Antibodies to purified brush-border PPH identified a major protein band at 120 kDa and a minor protein band at 195 kDa in solubilized jejunal brush border. Immunohistochemistry identified the enzyme only on the brush-border surface of the jejunum, whereas an immunoblot of solubilized brush-border membranes identified brush-border PPH in the jejunum but not in the ileum. The parallel of the regional location of in vivo hydrolysis of PteGlu3 with the location of brush-border PPH activity and immunoreactivity demonstrates the functional specificity of this enzyme in folate digestion.
    • "Dietary folates predominantly exist as polyglutamates, which have to be hydrolyzed to monoglutamates in order to be transported. The enzyme folylpoly-γ-glutamate carboxypeptidase (FGCP), that is anchored to the intestinal apical brush border and is encoded by the glutamate carboxypeptidase II (GCPII) gene, is responsible for this hydrolysis in the gut (Fig. 2) (Chandler et al. 1991). Monoglutamylated folates are subsequently absorbed in the duodenum and upper part of the jejunum by the high-affinity proton-coupled folate receptor PCFT1 (Qiu et al. 2006). "
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    • "The final pellet was re-suspended in 250 μL Tris buffer containing 1 × complete protease inhibitor (Sigma). BBMV enrichment was determined by a >20-fold increase in alkaline phosphatase activity as previously described (Chandler et al. 1991). Protein concentrations were determined using the Bradford assay (Bio-Rad). "
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