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

Islet neogenesis associated protein (INGAP) promotes the generation of new islet mass in adult animal models. It is not understood what factors control the expression of INGAP. In this study, factors that regulate the expression of INGAP promoter activity are reported. To determine factors that regulate INGAP expression, we previously cloned the promoter region for INGAP. Analysis of the INGAP promoter suggested that candidate regulators of INGAP expression include the transcription factors PDX-1, NeuroD, PAN-1, STAT and AP-1. Using gene addition experiments in the 293 cell line the activity of these transcription factors on an INGAP-promoter construct linked to the beta-galactosidase reporter has been determined. Induction of AP-1 activity or STAT activity using PMA or LIF stimulation respectively, or direct expression of PAN-1 specifically up-regulates INGAP promoter activity. In contrast, co-expression of PDX-1 but not NeuroD inhibits activation of the INGAP-promoter driven by PAN-1, PMA or LIF stimulation. PDX-1 binds directly to the INGAP promoter as determined in electromobility shift and antibody supershift assays. Expression of the INGAP-promoter-reporter construct in the HIT-T15 beta-cell line, a cell line that expresses endogenous PDX-1, did not reveal PMA-mediated stimulation of INGAP promoter activity. HIT-T15 cells however did efficiently transfect (> 68%) and respond (2-fold) to PMA-induced signal transduction to a transfected AP-1-CAT reporter. Partial reduction of PDX-1 expression in HIT-T15 cells was associated with recovery of PMA induced INGAP promoter activity. These data suggest that expression of PDX-1 is associated with a repression of stimulus-induced INGAP promoter activity that appears to be mediated by a direct DNA interaction. These findings implicate PDX-1 in a possible feedback loop to block unbridled islet expansion.
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PMID:PDX-1 can repress stimulus-induced activation of the INGAP promoter. 1652 40

The electrophoretic mobility and catalytic activity of individual molecules of Escherichia coli beta-galactosidase were measured using CE-LIF detection. Both the mobility and activity were reproducible for each molecule but differed between individual molecules. Assays were performed using uncoated capillaries and capillaries coated with different polymers, using enzymes from different sources and by three different experimental protocols. In all cases the observed ranges in electrophoretic mobilities were similar. The observed range in the electrophoretic mobility may be explained by structural microheterogeneity resulting in a gain or loss of up to 1.6 suppressed charge units. There was no observed relationship between the observed activities and electrophoretic mobilities. If the finding that individual beta-galactosidase molecules have heterogeneous electrophoretic mobility can be extended to other proteins, this may limit the resolution possible for capillary zone electrophoresis protein separations.
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PMID:Measurement of the differences in electrophoretic mobilities of individual molecules of E. coli beta-galactosidase provides insight into structural differences which underlie enzyme microheterogeneity. 1892 1

A CE-LIF detection-based assay was developed for the study of individual molecules of Escherichia coli beta-galactosidase. The assay allows for the simultaneous measurement of the electrophoretic mobility, catalytic activity and the variation in activity over time of individual enzyme molecules. In addition to showing the microheterogeneity of the enzyme molecules with respect to mobility and activity, it was demonstrated that at elevated temperatures the enzyme activity fluctuates over time. Incubation at varying temperatures showed that individual beta-galactosidase molecules exhibit differences in their change in activity upon a change in incubation temperature. Incubation at one temperature, followed by an incubation at an elevated temperature and subsequent incubation back at the initial lower temperature caused the molecules to have a different activity than they had initially. Additionally, thermal denaturation was found to cause a rapid and complete loss of activity.
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PMID:Continuous flow assay for the simultaneous measurement of the electrophoretic mobility, catalytic activity and its variation over time of individual molecules of Escherichia coli beta-galactosidase. 1901 4

The role of translation error for Escherichia coli individual beta-galactosidase molecule catalytic and electrophoretic heterogeneity was investigated using CE-LIF. An E. coli rpsL mutant with a hyperaccurate translation phenotype produced enzyme molecules that exhibited significantly less catalytic heterogeneity but no reduction of electrophoretic heterogeneity. Enzyme expressed with streptomycin-induced translation error had increased thermolability, lower activity, and no significant change to catalytic or electrophoretic heterogeneity. Modeling of the electrophoretic behaviour of beta-galactosidase suggested that variation of the hydrodynamic radius may be the most significant contributor to electrophoretic heterogeneity.
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PMID:Effect of alteration of translation error rate on enzyme microheterogeneity as assessed by variation in single molecule electrophoretic mobility and catalytic activity. 1944 45