Sucrose is a natural product occurs widely in nature. In living organisms such as plants, sucrose phosphate synthase (SPS) is the key rate-limiting enzyme for sucrose synthesis. SPS catalyzes the synthesis of sucrose-6-phosphate, which is further hydrolyzed by sucrose phosphatase to form sucrose. Researches on SPS in recent decades have been focused on the determination of enzymatic activity of SPS, the identification of the inhibitors and activators of SPS, the covalent modification of SPS, the carbohydrate distribution in plants regulated by SPS, the mechanism for promoting plant growth by SPS, the sweetness of fruit controlled by SPS, and many others. A systematic review of these aspects as well as the crystal structure and catalytic mechanism of SPS are presented.
Carbohydrate Metabolism ; Glucosyltransferases/metabolism* ; Plants/metabolism* ; Sucrose

OBJECTIVETo construct an acid-sensitive mutant of Streptococcus mutans (S. mutans) by transposon mutagenesis and to find a new gene related to the acid tolerance of S. mutans.

METHODSThe transposon Tn917 was delivered into S. mutans UA159 by the temperature-sensitive plasmid pTV1-OK bearing Tn917 and transposition of Tn917 was induced after incubation at non-permissive temperature (42 degrees C). Transposants harboring Tn917 in the chromosome were screened for the selection of mutant that had diminished growth at low pH. Southern analysis was performed with EcoRI (no cut within Tn917) digests of S. mutans UA159 and the selected aid-sensitive mutant, with DIG-labeled probe of 4.3 kb KpnI fragment of pTV1-OK containing Tn917. Genetic backcross experiment was performed by transforming the genome of the mutant to another S. mutans strain MT8148 to determine the linkage of Tn917 insertion to the change of phenotype (acid-sensitivity). Comparison of the abilities to grow at low pH, the glycolytic pH drop and killing pH values were done between the acid-sensitive mutant and the parent strain. The asymmetric PCR method was used to obtain the fragment flanking Tn917 and the PCR products were cloned to pMD18-T vector for sequencing.

RESULTSOne mutant that showed no growth at pH 5.0 was isolated from 2 316 transposants and was named as b23. Southern analysis and genetic backcross experiment confirmed the linkage between single Tn917 insertion into the chromosome and the phenotypic change (acid sensitive). b23 was less acid tolerant than UA159 in that it showed poorer growth at low pH and higher glycolytic pH minimum and higher killing pH. BLAST results indicated that Tn917 inserted into the genome of S. mutans UA159 at the site of 996 123 bp.

CONCLUSIONAn acid-sensitive mutant of S. mutans was successfully constructed and a new gene that is responsible for the acid tolerance in S. mutans UA159 was revealed.

Genes, Bacterial ; Streptococcus mutans ; genetics ; Sucrose ; metabolism

BACKGROUNDStreptococcus (S.) oligofermentans is a newly identified bacteria with a yet to be defined mechanism of sucrose metabolism that results in acid production. This study aimed to investigate the biochemical mechanisms of S. oligoferm-entans glucose metaolism.

METHODSThe S. oligofermentans LMG21532, Lactobacillus (L.) fermentum 38 and the S. mutans UA140 were used to characterize sucrose metabolism by measuring lactate dehydrogenase (LDH) activity and lactic acid production. Continuous dynamics and high performance capillary electrophoresis were used to determine LDH activity and lactic acid production, respectively, from bacteria collected at 0, 10 and 30 minutes after cultured in 10% sucrose.

RESULTSThese analyses demonstrated that LDH activity of the three bacterial strains examined remained stable but significantly different throughout the sucrose fermentation process. The S. oligofermentans LDH activity ((0.61 ± 0.05) U/mg) was significantly lower than that of L. fermentum ((52.91 ± 8.97) U/mg). In addition, the S. oligofermentans total lactate production ((0.048 ± 0.021) mmol/L) was also significantly lower than that of L. fermentum ((0.958 ± 0.201) mmol/L). Although the S. oligofermentans LDH production was almost double of that produced by S. mutans ((0.32 ± 0.07) U/mg), lactic acid production was approximately one sixth that of S. mutans ((0.296 ± 0.058) mmol/L). Additional tests examining pyruvic acid production (the LDH substrate) demonstrated that lactic acid concentrations correlated with pyruvic acid production. That is, pyruvic acid production by S. oligofermentans was undetectable following sucrose incubation, however, (0.074 ± 0.024) and (0.175 ± 0.098) mmol/L pyruvic acid were produced by S. mutans and L. fermentum, respectively.

CONCLUSIONS. oligofermentans is incapable of fermenting carbohydrates to produce enough pyruvic acid, which results in reduced lactic acid production.

L-Lactate Dehydrogenase ; metabolism ; Lactic Acid ; metabolism ; Pyruvic Acid ; metabolism ; Streptococcus ; metabolism ; Sucrose ; metabolism

OBJECTIVETo explore the role of µ-opioid receptors (MOR) in the central nucleus of the amygdala (CeA) in modulating sucrose solution intake in rats.

METHODSSprague-Dawley rats received intra-CeA injection of MOR agonist DAMGO or saline, and then underwent two bottle choice test between sucrose solution and distilled water. After intake of sucrose solution or distilled water, activated neurons in the CeA were labeled and identified with MOR/Fos-double labeling immunohistochemistry.

RESULTSCompared with saline injection, intra-CeA injection of DAMGO significantly increased sucrose solution intake in rats over a 3-h period. Sucrose solution intake induced significantly more c-Fos and MOR/Fos double-labeled neurons in the CeA than distilled water intake.

CONCLUSIONSThe CeA participates in modulation of sucrose intake in rats, and MOR may partly mediate this mechanism.

Amygdala ; metabolism ; Animals ; Male ; Neurons ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; metabolism ; Sucrose ; metabolism

STATEMENT OF PROBLEM: Streptococcus produces energy and forms extracellular polysaccharides by metabolizing sucrose. Insoluble glucan, a kind of extracellular polysaccharide, is the important material of dental plaque. Fructose affects the metabolism of sucrose. PURPOSE: The purpose of this study was to evaluate the effect of fructose on the metabolism of sucrose in Streptococcus mutans. MATERIALS AND METHODS: To determine the effect of fructose on the formation of artificial plaque by Streptococcus mutans Ingbritt, S. mutansand fructose were placed in beakers containing M17 broth and sucrose. The wires were hung on frameworks inserted into cork stoppers, and then immersed in each of the beakers. After the incubation with gentle shaking, each wire was weighed. To analyze the effect of fructose on the sucrose metabolism by S. mutans or glucosyltransferase, S. mutans and fructose were placed in M17 broth containing sucrose. After the incubation. the remaining sucrose and polymers were analysed by thin layer chromatography. RESULTS: The following results were obtained; 1. When Streptococcus mutans was cultured in the media containing 3% sucrose for 8 hours, the mean weight of formed artificial plaque on the wires was 124.3+/-3.0 mg, whereas being reduced to 20.7+/-10.2 mg in the media added with 3% sucrose and 4% fructose(p<0.05). 2. When the control containing glucose was added with sucrose, the optical density of Streptococcus mutans solution cultured for 24 hours was not increased compared with the control, while being increased by adding with fructose. 3. When Streptococcus mutanswas incubated in the media added with sucrose and fructose for 8 hours, the number of viable cells was increased compared with the media added with sucrose. 4. The amount of remained sucrose was increased in Streptococcus mutansculture supernatant of media added with sucrose and fructose than with sucrose only, but the amount of produced insoluble glucan was decreased. 5. The amounts of remained sucrose and produced soluble glucan were increased in the culture of glucosyltransferase-contained media added with sucrose and fructose than with sucrose only, but the amount of produced insoluble glucan was decreased. CONCLUSION: These results indicated that the sucrose metabolism and the production of insoluble glucan were inhibited in Streptococcus mutans by adding fructose in the media containing sucrose.
Chromatography, Thin Layer ; Dental Plaque ; Fructose* ; Glucose ; Metabolism* ; Polymers ; Polysaccharides ; Streptococcus mutans* ; Streptococcus* ; Sucrose*

STATEMENT OF PROBLEM: Streptococcus produces energy and forms extracellular polysaccharides by metabolizing sucrose. Insoluble glucan, a kind of extracellular polysaccharide, is the important material of dental plaque. Fructose affects the metabolism of sucrose. PURPOSE: The purpose of this study was to evaluate the effect of fructose on the metabolism of sucrose in Streptococcus mutans. MATERIALS AND METHODS: To determine the effect of fructose on the formation of artificial plaque by Streptococcus mutans Ingbritt, S. mutansand fructose were placed in beakers containing M17 broth and sucrose. The wires were hung on frameworks inserted into cork stoppers, and then immersed in each of the beakers. After the incubation with gentle shaking, each wire was weighed. To analyze the effect of fructose on the sucrose metabolism by S. mutans or glucosyltransferase, S. mutans and fructose were placed in M17 broth containing sucrose. After the incubation. the remaining sucrose and polymers were analysed by thin layer chromatography. RESULTS: The following results were obtained; 1. When Streptococcus mutans was cultured in the media containing 3% sucrose for 8 hours, the mean weight of formed artificial plaque on the wires was 124.3+/-3.0 mg, whereas being reduced to 20.7+/-10.2 mg in the media added with 3% sucrose and 4% fructose(p<0.05). 2. When the control containing glucose was added with sucrose, the optical density of Streptococcus mutans solution cultured for 24 hours was not increased compared with the control, while being increased by adding with fructose. 3. When Streptococcus mutanswas incubated in the media added with sucrose and fructose for 8 hours, the number of viable cells was increased compared with the media added with sucrose. 4. The amount of remained sucrose was increased in Streptococcus mutansculture supernatant of media added with sucrose and fructose than with sucrose only, but the amount of produced insoluble glucan was decreased. 5. The amounts of remained sucrose and produced soluble glucan were increased in the culture of glucosyltransferase-contained media added with sucrose and fructose than with sucrose only, but the amount of produced insoluble glucan was decreased. CONCLUSION: These results indicated that the sucrose metabolism and the production of insoluble glucan were inhibited in Streptococcus mutans by adding fructose in the media containing sucrose.
Chromatography, Thin Layer ; Dental Plaque ; Fructose* ; Glucose ; Metabolism* ; Polymers ; Polysaccharides ; Streptococcus mutans* ; Streptococcus* ; Sucrose*

OBJECTIVETo evaluate the effect of chewing sugar-free gum after sucrose challenge on dental plaque pH in situ.

METHODS16 healthy volunteers aged 23 - 32 years were screened as subjects. The pH of 48-hour dental plaque was measured using a Beetrode pH microelectrode when subjects chewed Extra sugar-free gum after sucrose challenge.

RESULTSDental plaque pH maintained at resting plaque pH when immediately chewed sugar-free gum after sucrose challenge. Chewing sugar-free gum at 5 min after sucrose challenge, dental plaque pH was raised from 5.59 (measured at 5 min after sucrose challenge) to 6.98 (measured at 10 min after sucrose challenge).

CONCLUSIONSChewing sugar-free gum after sucrose challenge can neutralize organic acid produced by bacteria in dental plaque and rapidly rise plaque pH.

Adult ; Chewing Gum ; Dental Plaque ; metabolism ; prevention & control ; Female ; Humans ; Hydrogen-Ion Concentration ; Male ; Sucrose

In order to investigate the enzyme production mechanism of yak rumen-derived anaerobic fungus Orpinomyces sp. YF3 under the induction of different carbon sources, anaerobic culture tubes were used for in vitro fermentation. 8 g/L of glucose (Glu), filter paper (Flp) and avicel (Avi) were respectively added to 10 mL of basic culture medium as the sole carbon source. The activity of fiber-degrading enzyme and the concentration of volatile fatty acid in the fermentation liquid were detected, and the enzyme producing mechanism of Orpinomyces sp. YF3 was explored by transcriptomics. It was found that, in glucose-induced fermentation solution, the activities of carboxymethyl cellulase, microcrystalline cellulase, filter paper enzyme, xylanase and the proportion of acetate were significantly increased (P < 0.05), the proportion of propionate, butyrate, isobutyrate were significantly decreased (P < 0.05). The results of transcriptome analysis showed that there were 5 949 differentially expressed genes (DEGs) between the Glu group and the Flp group, 10 970 DEGs between the Glu group and the Avi group, and 6 057 DEGs between the Flp group and the Avi group. It was found that the DEGs associated with fiber degrading enzymes were significantly up-regulated in the Glu group. Gene ontology (GO) function enrichment analysis identified that DEGs were mainly associated with the xylan catabolic process, hemicellulose metabolic process, β-glucan metabolic process, cellulase activity, endo-1,4-β-xylanase activity, cell wall polysaccharide metabolic process, carbohydrate catabolic process, glucan catabolic process and carbohydrate metabolic process. Moreover, the differentially expressed pathways associated with fiber degrading enzymes enriched by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were mainly starch and sucrose metabolic pathways and other glycan degradation pathways. In conclusion, Orpinomyces sp. YF3 with glucose as carbon source substrate significantly increased the activity of cellulose degrading enzyme and the proportion of acetate, decreased the proportion of propionate, butyrate and isobutyrate. Furthermore, the degradation ability and energy utilization efficiency of fungus in the presence of glucose were improved by means of regulating the expression of cellulose degrading enzyme gene and participating in starch and sucrose metabolism pathway, and other glycan degradation pathways, which provides a theoretical basis for the application of Orpinomyces sp. YF3 in practical production and facilitates the application of Orpinomyces sp. YF3 in the future.
Animals ; Cattle ; Neocallimastigales/metabolism* ; Anaerobiosis ; Rumen/microbiology* ; Propionates/metabolism* ; Isobutyrates/metabolism* ; Cellulose/metabolism* ; Fungi ; Starch/metabolism* ; Glucose/metabolism* ; Acetates ; Sucrose/metabolism* ; Cellulases ; Cellulase

Licorice seedlings were taken as experimental materials, an experiment was conducted to study the effects of exogenous sucrose on growth and active ingredient content of licorice seedlings under NaCl stress conditions. The results of this study showed that under salt stress conditions, after adding a certain concentration of exogenous sucrose, the licorice seedlings day of relative growth rate was increasing, and this stress can be a significant weakening effect, indicating that exogenous sucrose salt stress-relieving effect. The total flavonoids and phenylalanine ammonia lyase (PAL) activity were significantly increased, the exogenous sucrose can mitigated the seedling roots under salt stress, the licorice flavonoid content in the enhanced growth was largely due to the activity of PAL an increased, when the concentration of exogenous sucrose wae 10 mmol x L(-1), PAL activity reaching a maximum, when the concentration of exogenous sucrose was 15 mmol x L(-1), PAL activity turned into a downward trend, the results indicating that this mitigation has concentration effect. After applying different concentrations of exogenous sugar, the contents of liquiritin changes with the change of flavonoids content was similar. After applying different concentrations of exogenous sucrose, the content of licorice acid under salt stress was higher than the levels were not reached during salt stress, the impact of exogenous sucrose concentration gradient of licorice acid accumulation was not obvious.
Drugs, Chinese Herbal ; analysis ; metabolism ; Glycyrrhiza ; chemistry ; growth & development ; metabolism ; Plant Roots ; chemistry ; growth & development ; metabolism ; Seedlings ; chemistry ; growth & development ; metabolism ; Sodium Chloride ; metabolism ; Sucrose ; metabolism

Effects of sucrose concentrations and light on the growth and production of total isoflavones and puerarin in Pueraria phaseoloides hairy roots cultured onto solid MS media supplemented with 1%, 3%, 5%, 7% and 9% sucrose, respectively, were investigated. The results showed that among the sucrose concentrations tested, 3% sucrose in the medium enhanced the growth and stimulated accumulation of total isoflavones and puerarin in P. phaseoloides hairy roots, After cultured for 20 days, the biomass of hairy roots reached 0.48 g (DW dry weight)/flask and its contents of total isoflavones and puerarin were 25.44 mg/g (DW) and 11.64 mg/g (DW), respectively. In comparison with 3% sucrose, the dry weight proliferation of hairy roots cultured with 5% sucrose was increased by 7.0%, while cultured with 1%, 7% and 9% sucrose, the dry weight proliferation of hairy roots was decreased by 62.4%, 42.8% and 65.3%, their total isoflavones content was decreased by 57.4%, 13% and 33.4% and their puerarin content was decreased by 47.9%, 15.8% and 35.1%; but their content of total soluble sugars was increased 0.52, 1.45 and 1.54 times, respectively. Compared with hairy roots in blue light and white light, the biomass of hairy roots cultured in the dark for 30 days was 0.83 g (DW)/flask and was increased by 37.1% and 23.3%, respectively. The content of total isoflavones in hairy roots cultured in white light was as much as 1.15 times and 1.19 times that in blue light and in the dark, respectively. It was also observed that hairy roots cultured in blue light and white light partly became light green and that blue light could inhibit accumulation of puerarin in hairy roots and the puerarin content in hairy root cultured in white light and in the dark were 1.61 times and 1.52 times that in blue light, respectively.
Culture Media ; Isoflavones ; biosynthesis ; Light ; Plant Roots ; growth & development ; metabolism ; Pueraria ; growth & development ; metabolism ; Sucrose ; pharmacology ; Tissue Culture Techniques ; methods