Metabolic cardiomyopathy in GM1 gangliosidosis: Worse prognosis factor?

GM1 gangliosidosis is an autosomal recessive lysosomal storage disorder due to deficiency of the β-galactosidase enzyme which hydrolyzes the terminal β-galactosyl residues from GM1 ganglioside, glycoproteins, and glycosaminoglycans. Patients with infantile GM1 gangliosidosis present at birth or shortly thereafter with visceral changes and severe neurological deterioration leading to early death. In this report, we presented a case of infantile GM1 gangliosidosis associated with multiple organomegaly.

Beta galactosidases in Arabidopsis and tomato–a mini review

Beta galactosidases (BGALs) are glycosyl hydrolases that remove terminal β-D-galactosyl residues from β-D-galactosides. There are 17 predicted BGAL genes in the genomes of both Arabidopsis (BGAL1–17) and tomato (TBG1–17). All tested BGALs have BGAL activity but their distinct expression profiles and ancient phylogenetic separation indicates that these enzymes fulfil diverse, non-redundant roles in plant biology. The majority of these BGALs are predicted to have signal peptide and thought to act during cell wall-related biological processes. Interestingly, deletion of BGAL6 and BGAL10 in Arabidopsis causes reduced mucilage release during seed imbibition and shorter siliques respectively, whereas TBG4 depletion by RNAi decreases in fruit softening in tomato. The majority of plant BGALs remain to be characterized.

Classification, Substrate Specificity and Application of α-Galactosidases

Galactose is found in many oligosaccharides, galactomannans, glycoproteins and glycolipids, which are widely distributed in plants microorganisms and animals. α-Galactosidase (α-Gal) catalyzes the hydrolysis of 1,6-linked α-galactosyl residues and transgalactosylation. α-Gals are classified into four glycoside hydrolases families (GH): 4, 27, 36 and 57. The majority of known α-Gals belongs to GH families 27 and 36.α-Gals are of particular interest in view of their biotechnological applications.

Expression and Characterization of a Mycoplasma genitalium Glycosyltransferase in Membrane Glycolipid Biosynthesis

Mycoplasmas contain glycoglycerolipids in their plasma membrane as key structural components involved in bilayer properties and stability. A membrane-associated glycosyltransferase (GT), GT MG517, has been identified in Mycoplasma genitalium, which sequentially produces monoglycosyl- and diglycosyldiacylglycerols. When recombinantly expressed in Escherichia coli, the enzyme was functional in vivo and yielded membrane glycolipids from which Glcβ1,6GlcβDAG was identified as the main product. A chaperone co-expression system and extraction with CHAPS detergent afforded soluble protein that was purified by affinity chromatography. GT MG517 transfers glucosyl and galactosyl residues from UDP-Glc and UDP-Gal to dioleoylglycerol (DOG) acceptor to form the corresponding β-glycosyl-DOG, which then acts as acceptor to give β-diglycosyl-DOG products. The enzyme (GT2 family) follows Michaelis-Menten kinetics. kcat is about 5-fold higher for UDP-Gal with either DOG or monoglucosyldioleoylglycerol acceptors, but it shows better binding for UDP-Glc than UDP-Gal, as reflected by the lower Km, which results in similar kcat/Km values for both donors. Although sequentially adding glycosyl residues with β-1,6 connectivity, the first glycosyltransferase activity (to DOG) is about 1 order of magnitude higher than the second (to monoglucosyldioleoylglycerol). Because the ratio between the non-bilayer-forming monoglycosyldiacylglycerols and the bilayer-prone diglycosyldiacylglycerols contributes to regulate the properties of the plasma membrane, both synthase activities are probably regulated. Dioleoylphosphatidylglycerol (anionic phospholipid) activates the enzyme, kcat linearly increasing with dioleoylphosphatidylglycerol concentration. GT MG517 is shown to be encoded by an essential gene, and the addition of GT inhibitors results in cell growth inhibition. It is proposed that glycolipid synthases are potential targets for drug discovery against infections by mycoplasmas.

Substrate Specificities of α-Galactosidase from Rice

The α-galactosidase from rice cleaved not only α-D-galactosyl residues from the non-reducing end of substrates such as melibiose, raffinose and stachyose, but also liberated the terminal galactosyl residues attached O-6 position of the reducing-end mannosyl residue in mannobiose and mannotriose. In addition, the enzyme tore off the stubbed galactosyl residues attached inner-mannosyl residues in mannopentaose. It also could catalyze efficient degalactosylation of galactomannans, such as guar gum and locust bean gum.

(472) Yeast Expressed Tomato β-Galactosidases 1, 4, and 5 Have Activity against Synthetic and Plant-derived Cell Wall Substrates

Fruit softening occurs by several mechanisms, including modifications of cell wall structure by wall degrading enzymes. The most prominent change in tomato fruit pericarp wall composition is the loss of galactosyl residues throughout development and especially during ripening. In order to understand the role of galactosyl turnover in fruit softening, we successfully produced three recombinant tomato β-galactosidase/exo-galactanase (TBG) fusion proteins in yeast. TBG1, 4 and 5 enzyme properties and substrate specificities were assessed. Optimum pH of TBG1, 4 and 5 was 5.0, 4.0, and 4.5 and optimum temperature was 40∼50, 40, and 40 °C, respectively. The K ms for TBG1, 4 and 5 were 7.99, 0.09, and 2.42 mm, respectively, using p-nitrophenyl-β-D-galactopyranoside as substrate. Using synthetic and plant-derived substrates, TBG1 and 5 released galactosyl residues from 1 → 4 linkages. TBG4 released galactosyl residues from a wide range of plant-derived oligosaccharides and polysaccharides. Using tomato fruit cell wall material, TBG1, TBG4 and TBG5 released galactosyl residues from a variety of fruit stages and cell wall fractions. TBG4 released the most galactosyl residues from the ASP fraction and especially the ASP fraction from fruit at the turning stage. Interestingly, even though walls from Turning fruit stage contain less total galactosyl residues than at the Mature Green stage, TBG4 released 3–4 fold more galactose from the CSP and ASP fractions from Turning fruit. These results suggest that changes in structure of wall pectic polysaccharides leading up to the Turning stage may cause the wall to become more susceptible to hydrolysis by the TBG4 product.