Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of extracellular matrix as a determinant of intestinal cell maturation was explored by growing a normal, but immature, rat small intestinal cell line (IEC-6) on basement membrane extract from Engelbreth-Holm-Swarm (EHS) sarcoma cells (ECM). Grown on plastic or glass, these cells are relatively immature and proliferate rapidly. In contrast, cells on ECM attached more rapidly, stopped proliferating, and rapidly organized into multicellular complex structures. Ultrastructurally, cells grown on ECM displayed significantly more mitochondria, rough endoplasmic reticulum, apical microvilli, and complex golgi apparatus, consistent with greater maturity and synthetic activity. By indirect immunofluorescence, sucrase, alkaline phosphatase, and cellular apolipoprotein B were present in cells grown on ECM only. In contrast to cells grown on glass, these cells also demonstrated Na-dependent glucose absorption, a function unique to mature villus cells (7). We conclude that the basement membrane may be a key determinant of intestinal epithelial cell maturation. The development of a mature villuslike intestinal cell in vitro may have wide application for future studies of induction and regulation of intestinal maturation and function.
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PMID:Differentiation of rat small intestinal epithelial cells by extracellular matrix. 334 2

Hyperlipidemia arises from a disturbance in the balance between production and degradation of lipoprotein particles. Variation in the secretion of human apolipoprotein B (apoB), the major protein component of triglyceride-rich lipoproteins, directly affects this homeostasis. Naturally occurring apoB signal peptide variants (associated with hypertriglyceridemia, altered postprandial lipid metabolism, or atherosclerosis) were investigated for their ability to direct transit through the secretion pathway. Three apoB signal peptide isoforms were fused to the secretory protein, invertase, and expressed in yeast. A deletion or insertion in the hydrophobic core of the signal peptide mediated inefficient translocation into the endoplasmic reticulum and was secretion-defective, relative to the common 27-residue isoform. Additionally, the insertion apoB isoform was observed in yeast to confer a defect in export from the endoplasmic reticulum. Secretion of the apoB signal peptide-invertase fusions responded positively to an inhibitor of calpain type I proteases. These observations suggest that the apoB signal peptide plays a role in determining the levels of apoB degradation and secretion and, thus, hyperlipidemia.
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PMID:Human apolipoprotein B signal sequence variants confer a secretion-defective phenotype when expressed in yeast. 806 10

Based on titration microcalorimetry and Caco-2 cell line transfection studies, it has been suggested that the A54T of the FABP2 gene plays a significant role in the assimilation of dietary fatty acids. However, reports were divergent with regard to the in vivo interaction between this polymorphism and postprandial lipemia. We therefore determined the influence of this intestinal fatty acid-binding protein polymorphism on intestinal fat transport using the human jejunal organ culture model, thus avoiding the interference of various circulating factors capable of metabolizing in vivo postprandial lipids. Analysis of DNA samples from 32 fetal intestines revealed 22 homozygotes for the wild-type Ala-54/Ala-54 genotype (0.83) and 10 heterozygotes for the polymorphic Thr-54/Ala-54 genotype (0.17). The Thr-encoding allele was associated with increased secretion of newly esterified triglycerides, augmented de novo apolipoprotein B synthesis, and elevated chylomicron output. On the other hand, no alterations were found in very low density lipoprotein and high density lipoprotein production, apolipoprotein A-I biogenesis, or microsomal triglyceride transfer protein mass and activity. Similarly, the alanine to threonine substitution at residue 54 did not result in changes in brush border hydrolytic activities (sucrase, glucoamylase, lactase, and alkaline phosphatase) or in glucose uptake or oxidation. Our data clearly document that the A54T polymorphism of FABP2 specifically influences small intestinal lipid absorption without modifying glucose uptake or metabolism. It is proposed that, in the absence of confounding factors such as environmental and genetic variables, the FABP2 polymorphism has an important effect on postprandial lipids in vivo, potentially influencing plasma levels of lipids and atherogenesis.
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PMID:The polymorphism at codon 54 of the FABP2 gene increases fat absorption in human intestinal explants. 1148 82