Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.108 (lactase)
 2,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A genetically conditioned mouse model of exocrine pancreatic insufficiency (epi) has been used to study the effect of the absence of lumenal proteases on small intestinal mucosal proteins. The small bowel was divided into eight equal segments. Enzyme activity was increased only in the first three segments in the case of maltase, sucrase, and lactase (all mol wt above 200,000). Alkaline phosphatase (mol wt 145,000), trehalase (mol wt 95,000), and peptidase (mol wt 175,000) activities were unaffected in proximal segments from epi mice. Proximal brush border proteins were identified and measured quantitatively by sodium dodecyl sulfate acrylamide gel electrophoresis. Those enzymes with increased activity were associated with increased amounts of protein in epi mice. Double labeled studies of protein turnover revealed a longer half-life for large brush border proteins (mol wt above 175,000) in epi mice than in normal mice. Enterokinase activity (a marker for duodenal mucosa) was nearly absent from the duodenum of epi mice. Receptors for the intrinsic factor-vitamin B12 complex (markers for ileal mucosal) were present in the ileum equally in normal and in epi mice. Enterokinase activity can be induced in epi mice by feeding its substrate trypsinogen, but not by trypsin or chymotrypsinogen. Epi mice thus retain the ability to synthesize enterokinase. Pancreatic proteases play an important role in the turnover of certain large mucosal proteins and in the induction of enterokinase.
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PMID:Effect of exchange exocrine pancreatic insufficiency on small intestine in the mouse. 20 83

The concomitant appearance of enterokinase (EK) and trypsin activities in the human intestinal mucosa is indicative of the importance of EK as an activator of trypsinogen and therefore as the key enzyme in protein digestion. Enterokinase can be detected in fetal mucosa from the 26th week of gestation on, paralleling appearance of tryptic activity in meconium. The developmental pattern of EK activity increases with age. Between 26 to 30 weeks of gestation, the EK activity is only 6% and full term babies (40 weeks) 20% of that found in older children. In contrast, lactase studies during development show a lactase activity of only 30% in human fetuses between 26 to 34 weeks of gestation as compared to full term babies. During the same gestational period, sucrase and maltase activities reach 70% of the full term. In addition, the distributional pattern of EK differs from the disaccharidases, showing the highest activity in duodenum and the lowest in ileum, whereas disaccharidases are highest in jejunum with lower activity in duodenum and ileum. Differences in topographical distribution and time of appearance of EK and disaccharidases may be attributed to differences in orgin as well as subcellular localization of these enzymes. It is conceivable that the premature infant, between 26 to 30 weeks of gestation, is better equipped to deal with hydrolysis of alpha-glucosides than of lactose.
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PMID:Developmental pattern of small intestinal enterokinase and disaccharidase activities in the human fetus. 55 25

Neonates positive for immunoreactive trypsinogen assay (IRT) and negative for sweat test have formerly been found to carry the major cystic fibrosis (CF) mutation, delta F508, much more frequently than the general population. Among the 716 IRT positive newborns detected by a three tier (IRT, mutation analysis plus meconium lactase assay, sweat test) CF screening programme in north eastern Italy during the period January 1993 to March 1996, we found 45 carriers, a number significantly higher than the expected 17 (p < 0.001). We speculated that some of these heterozygotes could actually be affected by a very mild form of CF, and carry on the other chromosome an undetected CFTR mutation or a DNA variant, such as the 5-thymidine allele in intron 8 of the CFTR gene (IVS8-5T). This hypothesis was tested in four samples; group A (the 45 carriers mentioned above), group B (51 non-carrier, IRT positive neonates), group C (50 IRT negative neonates), and group D (90 CF adult female carriers). Chromosomes with IVS8-5T were seven (7.78%) in group A, seven (6.86%) in group B, five (5%) in group C, and four in group D (2.22%). The 5T prevalence in group A was significantly higher (p < 0.05) compared to group D; similarly, a higher (p < 0.05) 5T frequency in group A compared to group C was detected by considering the chromosomes free from CFTR mutations. This study is consistent with previous papers in finding among neonates with high trypsin levels a CF carrier frequency significantly higher than that expected. It is also suggested that in at least some babies raised trypsin levels at birth could be a phenotypic expression of compound heterozygosity for a major CF mutation plus IVS8-5T.
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PMID:CFTR mutations and IVS8-5T variant in newborns with hypertrypsinaemia and normal sweat test. 913 52