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

The sucrose operon of Clostridium beijerinckii NCIMB 8052 comprises four genes, which encode a sucrose-specific enzyme IIBC(Scr) protein of the phosphotransferase system (ScrA), a transcriptional repressor (ScrR), a sucrose hydrolase (ScrB) and an ATP-dependent fructokinase (ScrK). The scrARBK operon was cloned in Escherichia coli in three stages. Initial isolation was achieved by screening a C. beijerinckii genomic library in E. coli for clones able to utilize sucrose, while the remainder of the operon was isolated by inverse PCR and by plasmid rescue of flanking regions from a scrB mutant constructed by targeted gene disruption. Substrate specificity assays confirmed that the sucrose hydrolase was a beta-fructofuranosidase, able to hydrolyse sucrose and raffinose but not inulin or levans, and that the scrK gene encoded an ATP/Mg2+-dependent fructokinase. Both enzyme activities were induced by sucrose in C. beijerinckii. Disruption of the scr operon of C. beijerinckii by targeted plasmid integration into either the scrR or the scrB gene resulted in strains unable to utilize sucrose, indicating that this was the only inducible sucrose catabolic pathway in this organism. RNA analysis confirmed that the genes of the scr operon were co-transcribed on a 5 kb mRNA transcript and that transcription was induced by sucrose, but not by glucose, fructose, maltose or xylose. Primer extension experiments identified the transcriptional start site as lying 44 bp upstream of the scrA ATG start codon, immediately adjacent to the imperfect pelindrome sequence proposed to be a repressor binding site. Disruption of the scrR gene resulted in constitutive transcription of the upstream scrA gene, suggesting that ScrR encodes a transcriptional repressor which acts at the scrA operator sequence. The scrR gene is therefore itself negatively autoregulated as part of the polycistronic scrARBK mRNA
 ...
PMID:The genes controlling sucrose utilization in Clostridium beijerinckii NCIMB 8052 constitute an operon. 1041 Dec 73

Disaccharidases are important digestive enzymes whose activities can be reduced by iron deficiency. We hypothesise that this is due to reduced gene expression, either by impairment to enterocyte differentiation or by iron-sensitive mechanisms that regulate mRNA levels in enterocytes. Iron-deficient Wistar rats were generated by dietary means. The enzyme activities and kinetics of sucrase and lactase were tested as well as the activity of intestinal alkaline phosphatase (IAP)-II because it is unrelated to carbohydrate digestion. mRNA levels of beta-actin, sucrase, lactase, and the associated transcription factors pancreatic duodenal homeobox (PDX)-1, caudal-related homeobox (CDX)-2, GATA-binding protein (GATA)-4, and hepatocyte nuclear factor (HNF)-1 were measured by real-time PCR. Spatial patterns of protein and gene expression were assessed by immunofluorescence and in situ hybridization, respectively. It was found that iron-deficient rats had significantly lower sucrase (19.5% lower) and lactase (56.8% lower) but not IAP-II activity than control rats. Kinetic properties of both enzymes remained unchanged from controls, suggesting a decrease in the quantity of enzyme present. Sucrase and lactase mRNA levels were reduced by 44.5% and 67.9%, respectively, by iron deficiency, suggesting that enzyme activity is controlled primarily by gene expression. Iron deficiency did not affect the pattern of protein and gene expression along the crypt to villus axis. Expression of PDX-1, a repressor of sucrase and lactase promoters, was 4.5-fold higher in iron deficiency, whereas CDX-2, GATA-4, and HNF-1 levels were not significantly different. These data suggest that decreases in sucrase and lactase activities result from a reduction in gene expression, following from increased levels of the transcriptional repressor PDX-1.
 ...
PMID:Decreased sucrase and lactase activity in iron deficiency is accompanied by reduced gene expression and upregulation of the transcriptional repressor PDX-1. 1608 62

In the Salmonella antigenic pattern, more than one phase of flagellar antigen is observed. The phase of flagellar antigen depends of the gene which encodes the protein building the filament of flagella. The fliC gene encodes the 1st phase of flagellar antigen and the fljB gene encodes the 2nd phase of flagellar antigen. The third phase of flagellar antigen is encoded by one of the genes localized on the plasmid. Expression of the fljB gene (part of the hinfljBA operon) is regulated by a mechanism of DNA fragment sequence inversion. The hin gene, which encodes Hin invertase, flanked by two regions - hixL and hixR - is inverted by Hin invertase together with Fis protein. This process turns on or turns off of the hinfljBA operon. When this operon is turned on, FljB protein is produced (structural protein of flagella filament), and also FljA protein, which is a transcriptional repressor of the fliC gene. This means that one Salmonella cell could have only one phase flagellar antigen--1st or 2nd phase. Sometimes, due to mutation in one of the mentioned genes, naturally diphasic Salmonella strains have the ability to produce only one phase of flagellar antigen. Mostly monophasic Salmonella with an active fliC gene are observed. In recent years such a strain, Salmonella enterica with the antigenic formula 1,4,[5],12: i: -, is one of the most often isolated strains from human cases in many European countries.
 ...
PMID:[Salmonella multiphasic flagellar antigen]. 2292 44