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Melibiose

About: Melibiose is a research topic. Over the lifetime, 1002 publications have been published within this topic receiving 27300 citations. The topic is also known as: Melibiose.


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Journal ArticleDOI
TL;DR: The findings strongly suggest that OsAkalphaGal is a thylakoid membrane-degrading enzyme involved in the degradation of digalactosyl diacylglycerol during rice leaf senescence.
Abstract: Here, we studied the functional role of a chloroplast alkaline alpha-galactosidase (OsAkalphaGal) in the breakdown of thylakoid membranes during rice (Oryza sativa) leaf senescence. We assayed the enzyme activity of recombinant OsAkalphaGal with different natural substrates and examined the effect of ectopic OsAkalphaGal expression in rice plants. Recombinant OsAkalphaGal showed at least a two-fold greater substrate-binding affinity and a 10-fold greater turnover rate to galactolipid digalactosyl diacylglycerol than the raffinose family of oligosaccharides (verbascose, stachyose, raffinose) and melibiose. The OsAkalphaGal null mutant (osakalphagal) displayed a delayed leaf senescence phenotype. OsAkalphaGal complementation in osakalphagal recovered OsAkalphaGal expression and showed a senescence phenotype similar to that of wild-type plants. Transgenic plants overexpressing OsAkalphaGal (UbiP-OsAkalphaGal) exhibited retarded plant growth and development, and showed a pale-green phenotype coupled with a reduced chlorophyll content to 42% in newly unfolded leaves. UbiP-OsAkalphaGal leaves also showed a 29-fold increase in alkaline alpha-galactosidase activity compared with wild-type leaves. An ultrastructural study of Ubi-OsAkalphaGal chloroplasts in newly unfolded leaves revealed abnormal grana organization. Our findings strongly suggest that OsAkalphaGal is a thylakoid membrane-degrading enzyme involved in the degradation of digalactosyl diacylglycerol during rice leaf senescence.

35 citations

Journal ArticleDOI
TL;DR: Two alpha-D-galactosidases produced by Aspergillus tamarii were purified from the mycelial extract by a procedure including chromatography on hydroxyapatite, DEAE- cellulose and ECTEOLA-cellulose, and each of these enzymes showed a single protein band corresponding to the alpha- D-galactsosidase activity when examined by polyacrylamide-gel electrophoresis.
Abstract: Two alpha-D-galactosidases (alpha-D-galactoside galactohydrolase, EC 3.2.1.22) produced by Aspergillus tamarii were purified from the mycelial extract by a procedure including chromatography on hydroxyapatite, DEAE-cellulose and ECTEOLA-cellulose. Each of these enzymes showed a single protein band corresponding to the alpha-D-galactosidase activity when examined by polyacrylamide-gel electrophoresis. They catalysed the hydrolysis of o-nitrophenyl alpha-D-galactoside, melibiose, raffinose and stachyose, but did not attack the galactomannans. Their Mr values were respectively 265000 +/- 5000 and 254000 +/- 5000 by the method of Hedrick & Smith [(1968) Arch. Biochem. Biophys. 126, 155-164]. Polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate in each case showed a single protein band, with Mr 88000 and 77500 respectively. The purified enzymes contained carbohydrate, consisting of N-acetylglucosamine, mannose, glucose and galactose in the estimated molar proportions of 1:9:5:8 in alpha-galactosidase I.

35 citations

Journal Article
TL;DR: The production of thermostable extracellular protease by Bacillus stearothermophilus Fl was influenced by the composition of culture medium and the presence of the metal ion at 4.5 mM enhanced the yield by two folds.
Abstract: The production of thermostable extracellular protease by Bacillus stearothermophilus Fl was influenced by the composition of culture medium. Peptone iv derived from soybean was the best organic compound for enzyme production. Sodium nitrate, ammonium salts and amino acids as sole nitrogen sources interfered with protease formation. The addition of most carbon sources to the peptone medium failed to improve the enzyme production. However, protease production was enhanced in the presence of melibiose and trehalose in sodium nitrate medium. Although the protease production was calcium independent, the presence of the metal ion at 4.5 mM enhanced the yield by two folds.

35 citations

Journal ArticleDOI
TL;DR: It is suggested that the fast transient response reflects charge transfer within MelB during cosubstrate binding while the slow component is associated with charge transfer across the proteoliposome membrane.
Abstract: Electrogenic activity associated with the activity of the melibiose permease (MelB) of Escherichia coli was investigated by using proteoliposomes containing purified MelB adsorbed onto a solid-supported membrane. Transient currents were selectively recorded by applying concentration jumps of Na+ ions (or Li+) and/or of different sugar substrates of MelB (melibiose, thio-methyl galactoside, raffinose) using a fast-flow solution exchange system. Characteristically, the transient current response was fast, including a single decay exponential component (τ ≈ 15 ms) on applying a Na+ (or Li+) concentration jump in the absence of sugar. On imposing a Na+ (or Li+) jump on proteoliposomes preincubated with the sugar, a sugar jump in a preparation preincubated with the cation, or a simultaneous jump of the cation and sugar substrates, the electrical transients were biphasic and comprised both the fast and an additional slow (τ ≈ 350 ms) decay components. Finally, selective inactivation of the cosubstrate transloca...

34 citations

Journal ArticleDOI
TL;DR: Examination of the lectin binding with 34 glycans revealed that it reacted strongly with the following glycoforms: most human blood group precursor (equivalent) glycoproteins (gps), two Galα1→4Gal-containing gps, and twod-galacturonic acid (GalUA)-containing polysaccharides (pectins from apple and citrus fruits), but poorly with most humanBlood group A and H active and sialylated gps.

34 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20236
202212
202112
202017
201913
201816