Dextrinases

The levels of limit dextrinase in germinating rye have been monitored.  

A carbohydrase-free limit dextrinase from malted sorghum flour readily 

The affinity chromatography of lysozymes on glycose-substituted agaroses has been investigated.  

Quantitative kinetic studies of lysozyme-catalysed hydrolyses can be achieved only in limited circumstances for example, the use of chromophoric substrates is beset by difficulties and no substrate of low molecular weight has gained acceptance in standard assays. An efficient and rapid assay of the lysozyme-catalysed hydrolysis and transglycosylation of [ C]chito-oligosaccharides uses h.p.l.c. to separate the products and liquid scintillation counting to determine their concentrations. 

Assays of lysozyme by a diffusion technique, which employs an agarose gel impregnated with substrate organisms (lysoplates), differed greatly from those obtained by spectrophotometric and immunological techniques. Different agaroses had unpredictable effects on the determination of lysozyme in normal 

The selective solubilization of a-D-glucosidases from the complex mixture of such enzymes in porcine intestinal mucosa led to the conclusion that separate enzymes are involved in the hydrolysis of isomaltose and the a-limit dextrins formed from starch by a-amylase ( isomaltase and limit dextrinase respectively). Various aspects of the enzymology of oligo-l,6-D-glucosidase (limit dextrinase ) from peas have been reported.  

The use of optical rotatory dispersion in quantitative analysis has been applied to the microdetermination of lysozyme. A spin-label assay for lysozyme which is based on the enzymic hydrolysis of spin-labelled peptidoglycan has been described. Hydrolysis of this polymer by lysozyme results in sharpening of the e.s.r. spectrum. According to this method, human lysozyme is 3.5 times as active as hen egg-white lysozyme. The assay is suitable for measuring lysozyme levels in biological fluids. 

Human and hen egg-white lysozymes have been shown to convert the Micrococcus luteus peptidoglycan into the disaccharide and tetrasaccharide of glycopeptide (14) and the peptide itself. With goose egg-white lysozyme, 

Lysozyme has been purified from human tears, serum, and urine of acute monocytic leukaemia patients, renal disease patients, and residents in cadmium-polluted areas of Tsushima Island, using affinity chromatography on an adsorbent containing lysozyme-lysate of Micrococcus lysodeikticus cell walls. The specific activities and heterogeneities of the preparations on disc gel electrophoresis were found to differ from one source of enzyme to another. 

Elevated levels of serum lysozyme have been observed in cases of Gaucher disease this high level was considered to reflect an increased body mass of reticuloendothelial cells. It was suggested that the enzyme elevation might be of use in diagnosis of Gaucher disease. In cases of monocytic leukaemia, myelomonocytic leukaemia, and myeloma no evidence has been found for immunoglobulin (IgG)-lysozyme complexes. The mobility of the serum lysozyme was identical to that of free urinary lysozyme. 

Gibberellic acid induced the de novo synthesis of limit dextrinase in barley grains with excised embryos.  

Suzuki and T. Kaneko, Agric. and Biol. Chem. Japan), 1976, 40, 577. 

A limit dextrinase isolated from broad-bean ( Vicia fabd) flour readily hydrolysed branched a-dextrins containing maltosyl or maltotriosyl side-chains, pullulan, and amylopectin j6-limit dextrin, whereas it hydrolysed glycogen -limit dextrin and amylopectin slowly and glycogens not at all.  

The substrate specificities of purified limit dextrinases from ungerminated oats (Avena sativa) and rice Oryza sativd) have been compared with that of a bacterial isoamylase/ The cereal enzymes are able to hydrolyse a-(l 6)-D-glucosidic linkages in oligosaccharides, a-dextrins, pullulan, amylopectin, and the -limit dextrins of amylopectin and glycogen, but are unable to hydrolyse glycogens. 

A sensitive fluorometric assay for lysozyme uses as the substrate Bacillus subtilis cell walls that have been labelled with fluorescamine on the free amino-groups of the diaminopimelic acid residues. The method is particularly suitable for measuring the competition between cell-wall preparations for the same enzyme. 

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This enzyme [EC 3.2.1.10] (also referred to as oUgo-1,6-glucosidase, sucrase-isomaltase, and limit dextrinase) catalyzes the hydrolysis of l,6-o -D-glucosidic linkages in isomaltose and dextrin products generated from starch and glycogen via a-amylase. See also Sucrase... 

The majority of dextrans in nature are produced extracellularly via dextran-sucrase from sucrose by several lactic acid bacteria, principally Leuconostoc and Streptococcus species [13]. Dextran is also synthesised by dextrinase of different Gluconobacter species [56]. Referring to this enzyme, fermentation of maltodextrins leads to a- —4) branched dextrans with comparatively lower Mw. However, dextransucrase from Leuconostoc mesenteroid.es NRRL B-512F has attracted most interest because of commercial use. 

The latest International Union Biochemicals report includes an enzyme 3.2.1.41 a-dextrin endo-l,6-a-glucosidase, other names limit dextrinase, amylopectin 6-glucanohydrolase, pullulanase. 

Dohlert and Knutson (1991) and D. J. Manners (personal communication) reported that extracts of sugary maize contain a mixture of limit dextrinase and isoamylase. However, James et al. (1995) reported that su 1 codes for the isoamylase. 

The plant and bacterial enzymes capable of hydrolyzing pullulan do not have identical specificities. In particular, the plant enzymes have little or no action on glycogen and phytoglycogen under conditions in which they readily hydrolyze amylopectin and its /3-dextrin. To stress this difference (the bacterial enzymes are capable of degrading both glycogen and phytoglycogen), Manners (1997) recommended different nomenclature for bacterial enzymes, to be called pullulanase, and the plant enzymes, to be called limit dextrinases. 

Gluco-oligosaccharides (GlcOS) can be made by the action of an enzyme, dextran dextrinase produced by Gluconobacter oxydans on maltodextrins. They have been made in whole-cell bioreactors [104] and evaluated in fecal batch cultures [105] and in three-stage gut models [106]. Mountzouris et al. [104] used methylation analysis to determine the linkages of... 

Dextrinases, a-glucosidases, and disaccharidases located on the surface of the brush border of the intestinal epithelial cell complete the conversion of starch to glucose. 

An a-dextrinase cleaves a-1,6 linkages, releasing glucose residues from branched oligosaccharides. 

Dextrinases - Sugar beet refining, juice processing. 

The limit-dextrinase activity of malted barley is important in distilhng and brewing, since its activity controls the conversion of starch into fermentable sugars. ... 

Broad-bean limit-dextrinase, originally termed R-enzyme, has been used for the structural analysis of a-dextrins for example, 6 -a-maltosylmalto-triose [0-a-n-glucopyranosyl-(l—>4)-0-a-D-glucopyranosyl-(l- 6)-0-a-n-... 

Alpha-dextrin endo-1,6-alpha-glucosidase. Pullulanase. Pullulan 6-glucanohydrolase. Limit dextrinase. Debranching enzyme. 3.2.1.41 Starch-debranching enzyme, hydrolyses (l-6)-alpha-glucosidic linkages in pullulan and starch to form maltotriose. 

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