Disease relevance of ISOMALTOSE

• The crystal structures of Klebsiella pneumoniae pullulanase and its complex with glucose (G1), maltose (G2), isomaltose (isoG2), maltotriose (G3), or maltotetraose (G4), have been refined at around 1.7-1.9A resolution by using a synchrotron radiation source at SPring-8 [1].
• A recombinant isomaltodextranase (1,6-alpha-D-glucan isomaltohydrolase; EC 3.2.1.94) from an Arthrobacter sp. that hydrolyzes dextrans to generate isomaltose was purified and crystallized using the sitting-drop vapour-diffusion method at 293 K [2].
• Inhibition by maltose, isomaltose, and nigerose of the synthesis of high-molecular-weight D-glucans by the D-glucosyltransferases of Streptococcus sobrinus [3].
• We recently reported that inositol dehydrogenase (EC 1.1.1.18) from Bacillus subtilis can catalyze the highly stereoselective oxidation of 1l-4-O-substituted myo-inositol derivatives, as well as disaccharides melibiose and isomaltose, but not gentiobiose or maltose, consistent with the requirement of an alpha-(1-->6) linkage [4].
• Recombinant AglA (EC 3.2.1.10) and AglB (EC 3.2.1.20), expressed in Escherichia coli, showed high hydrolytic activity towards isomaltose and pnp-alpha-glucoside [5].

High impact information on ISOMALTOSE

• A similar rate of hydrolysis of isomaltose by both isozymes was found indicating that the reduced catalytic activity of the variant isozyme toward glycogen is not the result of a reduced ability of this enzyme to cleave the alpha-1,6 linkages of glycogen [6].
• A comparison of metabolic profiles of non-stressed and stressed microspores using gas chromatography/mass spectrometry (GC/MS) identified 70 compounds, partly displaying significant changes in metabolite levels, e.g., highly elevated levels of isocitrate and isomaltose in stressed microspores compared to non-stressed microspores [7].
• The pH optimum of maltose-, starch- and isomaltose-hydrolysing activity was 6.5 and that of sucrose-hydrolysing activity 5 [8].
• The Val216 mutant was altered to hydrolyze both maltose and isomaltose but neither the Gly217 nor the Ser218 mutant changed their substrate specificity, indicating that Val216 is an important residue discriminating the alpha-1,4- and 1,6-glucosidic linkages of substrates [9].
• There was also an inverse correlation between peak glucose yield and ratio of initial rate of isomaltose production from glucose condensation to that of glucose production from maltodextrin hydrolysis [10].

Biological context of ISOMALTOSE

• Glucoamylase mutations to reduce isomaltose formation from glucose condensation and thus increase glucose yield from starch hydrolysis were designed to produce minor changes in the active site at positions not totally conserved [11].
• Identification and quantification of the plasma volume expander dextran in human urine by liquid chromatography-tandem mass spectrometry of enzymatically derived isomaltose [12].
• The dextran polymer was enzymatically hydrolysed by alpha-1,6-glucosidase (dextranase) followed by acetylation of the generated isomaltose subunits, allowing the chromatographic separation of different disaccharides, such as lactose, saccharose and isomaltose, as well as the identification and quantification of the analyte in human urine [12].

Anatomical context of ISOMALTOSE

• The degradation of glycogen in the lysosomes of newborn rat hepatocytes: glycogen-, maltose- and isomaltose-hydrolyzing acid alpha glucosidase activities in liver [13].

Associations of ISOMALTOSE with other chemical compounds

• Finally, the Asp309-->Asn mutation decreases the kcat for isomaltose hydrolysis around 200-fold, but only 30-fold for maltose [14].
• AgdB was a heterodimeric protein comprising 74- and 55-kDa subunits and catalyzed hydrolysis of maltose along with formation of isomaltose and panose [15].
• Analysis of linkage specificity using a number of substrates indicated a preferential hydrolysis of isomaltose (alpha1,6) with much less activity on nigerose (alpha1,3) and maltose (alpha1,4) [16].
• Based on models of isolated molecules of isomaltose and gentiobiose, the predicted Boltzmann-weighted nmr coupling constants were satisfactory, as were predicted optical rotations for gentiobiose [17].
• The action on isoprimerose by Asp. niger alpha-glucosidase was completely the same as that on isomaltose at optimum pH, optimum temperature, inhibition pattern of hydrolyzing activity by 1-deoxynojirimycin, and transfer action pattern [18].

Gene context of ISOMALTOSE

• Maltase which hydrolyzes the alpha-1,4-disaccharide, maltose, and the alpha-1,6-disaccharide, isomaltose, catalyzes the formation of both maltose and isomaltose from free glucose [19].
• Since only the alpha-1,6 linked isomaltose was detected as the transferase product, it was thought that the alpha-glucosidase was capable of glucosyl transfer via alpha-1,6-glucosidic bonds [20].

References