Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A dual enzyme electrode is explored for measuring lactulose in milk. A ring electrode (diameter = 3 mm; ring width = 10-20 microns) is proposed onto which tetrathiafulvalen-tetracyanoquinodimetane (TTF-TCNQ) salt was physically packed. The electrode is a band electrode with dimensions approaching those for micro electrodes, so that the improved faradaic current/charging current ratio lead to improved detection limits. Fructose dehydrogenase (FDH) and beta-galactosidase (beta-gal) were immobilized by covering the electrode surface with a dialysis membrane. Lactulose was hydrolyzed to D-fructose and D-galactose by beta-gal. The hydrolyzed D-fructose was oxidized by FDH which was simultaneously reduced to the reduced form (FDH-PQQH2). The FDH-PQQH2 was directly reoxidized by TTF-TCNQ on the ring electrode, whose current was monitored at 200 mV vs Ag/AgCl. The detection limit of the lactulose sensor was 1.0 microM and the selectivity for lactulose was at least 1000 times higher than that for lactose. Pasteurized, UHT and sterilized milks were applied to the lactulose sensor, showing good accuracy and precision and, furthermore, good correlation to a reference photometric method, even though no rigorous procedure for the electrode fabrication has presently been addressed.
 ...
PMID:A lactulose sensor based on coupled enzyme reactions with a ring electrode fabricated from tetrathiafulvalen-tetracyanoquinodimetane. 983 88

Lactulose is a disaccharide derived from lactose. There has been recent rekindling of interest in the possible benefits of pro- and prebiotics: mainly, lactic acid-producing bacteria and lactulose for the lower intestine. Since lactose maldigestion is a common genetic trait, we undertook this study to delineate similar effects between these two disaccharides. Nine healthy lactose maldigesting subjects underwent two separate periods of three weeks adaptation, first with 10 g twice daily lactulose and then 1.5 g twice daily lactose (in milk). Adaptation was defined by reduced breath Hydrogen (BH2) and symptoms after 50 g lactose challenges. In six subjects fecal beta-galactosidase was measured. All subjects consumed some lactose daily. In the first period, eight subjects improved symptoms and reduced BH2 significantly, while in the second period they did not. Fecal beta-galactosidase significantly increased after lactulose. This study supports the notion that lactulose and lactose may have similar clinical effects.
 ...
PMID:Improved parameters of lactose maldigestion using lactulose. 1147 4

The enzymatic transgalactosylation from lactose to fructose leading to the prebiotic disaccharide lactulose was investigated using the beta-galactosidase from Aspergillus oryzae and the hyperthermostable beta-glycosidase from Pyrococcus furiosus (CelB). The conditions for highest lactulose yields relative to the initial lactose concentration were established on a 1 mL scale. Dependent on the initial molar ratio of lactose to fructose, more or fewer oligosaccharides other than lactulose were generated. Bioconversions on a 30 mL scale in a stirred glass reactor were performed, and lactulose yields of 46 mmol/L (44% relative to lactose) for CelB and 30 mmol/L (30% relative to lactose) for A. oryzae beta-galactosidase were achieved. Only <5% of other oligosaccharides were detectable. The corresponding productivities were 24 and 16 mmol/L/h, respectively. The molecular structure of lactulose was investigated in detail and confirmed after purification of the reaction solution by LC-MS and 1D and 2D NMR. Lactulose (4-O-beta-D-galactopyranosyl-D-fructose) was unambiguously proved to be the major transglycosylation disaccharide.
 ...
PMID:Enzymatic production and complete nuclear magnetic resonance assignment of the sugar lactulose. 1553 7

We used DNA microarrays to measure transcription and iTRAQ 2D liquid chromatography-mass spectrometry/mass spectrometry (a mass-tag labeling proteomic technique) to measure protein expression in 14 strains of Escherichia coli adapted for hundreds of generations to growth-limiting concentrations of either lactulose, methylgalactoside, or a 72:28 mixture of the two. The two ancestors, TD2 and TD10, differ only in their lac operons and have similar transcription and protein expression profiles. Changes in transcription and protein expression are observed at 30-250 genes depending on the evolved strain. Lactulose specialists carry duplications of the lac operon and show increased transcription and translation at lac. Methylgalactoside specialists are galS(-) and so constitutively transcribe and translate mgl, which encodes a transporter of methylgalactoside. However, there are two strains that carry lac duplications, are galS(-), and show increased transcription and translation at both operons. One is a generalist, the other a lactulose specialist. The generalist fails to sweep to fixation because its lac(+), galS(+) competitor expresses the csg adhesin and sticks to the chemostat wall, thereby preventing complete washout. Transcription and translation are sometimes decoupled. Lactulose-adapted strains show increased protein expression at fru, a fructose transporter, without evidence of increased transcription. This suggests that fructose, produced by the action of beta-galactosidase on lactulose, may leach from cells before being recouped. Reduced expression, at "late" flagella genes and the constitutive gat operon, is an adaptation to starvation. A comparison with two other long-term evolution experiments suggests that certain aspects of adaptation are predictable, some are characteristic of an experimental system, whereas others seem erratic.
 ...
PMID:Transcription, translation, and the evolution of specialists and generalists. 1970 26