The conversion of group B red blood cells into group O by an alpha-D-galactosidase from taro (Colocasia esculenta)

Structure-function analysis of bacterial GH31 α-galactosidases specific for α-(1→4)-galactobiose

Glycoside hydrolase family 31 (GH31) contains α-glycoside hydrolases with different substrate specificities involved in various physiological functions. This family has recently been classified into 20 subfamilies using sequence similarity networks. An α-galactosidase from the gut bacterium Bacteroides salyersiae (BsGH31_19, which belongs to GH31 subfamily 19) was reported to have hydrolytic activity against the synthetic substrate p- nitrophenyl α-galactopyranoside, but its natural substrate remained unknown. BsGH31_19 shares low sequence identity (around 20%) with other reported GH31 α-galactosidases, PsGal31A from Pseudopedobacter saltans and human myogenesis-regulating glycosidase (MYORG), and was expected to have distinct specificity. Here, we characterized BsGH31_19 and its ortholog from a soil Bacteroidota bacterium, Flavihumibacter petaseus (FpGH31_19), and demonstrated that they showed high substrate specificity against α-(1→4)-linkages in α-(1→4)-galactobiose and globotriose [α-Gal-(1→4)-β-Gal-(1→4)-Glc], unlike PsGal31A and MYORG. The crystallographic analyses of BsGH31_19 and FpGH31_19 showed that their overall structures resemble those of MYORG and form a dimer with an interface different from that of PsGal31A and MYORG dimers. The structures of FpGH31_19 complexed with d-galactose and α-(1→4)-galactobiose revealed that amino acid residues that recognize a galactose residue at subsite +1 are not conserved between FpGH31_19 and BsGH31_19. The tryptophan (Trp153) that recognizes galactose at subsite -1 is homologous to the tryptophan residues in MYORG and α-galactosidases belonging to GH27, GH36, and GH97, but not in the bacterial GH31 member PsGal31A. Our results provide structural insights into molecular diversity and evolutionary relationships in the GH31 α-galactosidase subfamilies and the other α-galactosidase families.

Hooked on α-d-galactosidases: from biomedicine to enzymatic synthesis

α-d-Galactosidases (EC 3.2.1.22) are enzymes employed in a number of useful bio-based applications. We have depicted a comprehensive general survey of α-d-galactosidases from different origin with special emphasis on marine example(s). The structures of natural α-galactosyl containing compounds are described. In addition to 3D structures and mechanisms of action of α-d-galactosidases, different sources, natural function and genetic regulation are also covered. Finally, hydrolytic and synthetic exploitations as free or immobilized biocatalysts are reviewed. Interest in the synthetic aspects during the next years is anticipated for access to important small molecules by green technology with an emphasis on alternative selectivity of this class of enzymes from different sources.

Purification and characterization of alpha-D-galactosidase produced by ADG cell line established from abalon digestive gland

ADG cell line was established from an abalonedigestive gland and previously characterized. ADGcells have the potential to grow in protein-freeculture and secrete l3 types of glycosidases. Inthis article, we determined the origin of ADG cell line,using electron microscopy, and purified a glycosidasesecreted by these cells. The electron microscopicanalysis showed that ADG cell line contains severalnuclei, which suggests that they may be derived fromprotist cells. Moreover, alpha-D-galactosidasethat hydrolyzes p-nitorophenyl galactopyranosidewas purified 130-fold from the spent culture medium ofADG cells. The molecular weight of the enzyme,determined by sodium dodecyl sulfate polyacrylamidegel electrophoresis and gel filtration analysis, wasshown to be 43 and 42 kDa, respectively, and itappeared to consist of a single polypeptide chain. The purified enzyme preparation was practically freefrom other glycosidases secreted from the cells. Catalytic activity was optimal at pH 5.5 and at atemperature of 37 degrees C. The enzyme was also the most stable at pH 5.5.

Carbohydrase activities of the rolC-gene transformed and non-transformed ginseng cultures

The levels of activity of beta-D-glucosidase, alpha-D-mannosidase, alpha- and beta-D-galactosidase, 1,3-, 1,6-, 1,4-beta-D-glucanases, 1,4-alpha-D-glucanase, fucoidanhydrolase and agarase were measured in extracts of non-transgenic and transgenic Panax ginseng cultures transformed with the rolC gene. Significantly increased levels of activity of beta- and alpha-D-galactosidases and 1,3-beta-D-glucanase were detected in rolC-gene transformed cells, compared to the control non-transformed cells, while levels of activity of other enzymes were unchanged. These, as well as the gel-permeation experiments, revealed that transformation of ginseng cells by the rolC gene could significantly affect activity of some carbohydrases and production of their molecular forms.

Transfusion to blood group A and O patients of group B RBCs that have been enzymatically converted to group O

BACKGROUND

The transfusion of ABO-incompatible RBCs is the leading cause of fatal transfusion reactions. Group O RBCs, lacking terminal immunodominant A and B sugars to which humans are immunized, are safe for transfusion to persons of any ABO blood group. With the use of a recombinant alpha-galactosidase to remove terminal galactose from group B RBCs, the safety and efficacy of enzyme-converted group-B-to-group-O (ECO) RBC components were studied in transfusion-dependent patients.

STUDY DESIGN AND METHODS

Twenty-four patients (blood groups A and O) were randomly assigned to receive transfusion(s) of either ECO or control group O RBCs. If a second transfusion was given, the other blood component was administered.

RESULTS

Twenty-one patients were given ECO RBCs; 18 also underwent control transfusions. One patient received only a small aliquot for RBC survival studies, instead of a full-unit transfusion, because his serum was incompatible with ECO RBCs. No adverse events occurred. Both ECO and control transfusions resulted in appropriate Hb increments and comparable (51)Cr-labeled RBC survival studies. One patient developed a transient, weak-positive DAT, without hemolysis. Two weeks after transfusion, 5 of 19 evaluable ECO RBC recipients had increases in anti-B titers.

CONCLUSION

ECO RBCs were comparable to group O cells for safety and efficacy in this study. The clinical significance of the increase in anti-B and of occasional serologic incompatibilities with ECO RBCs is unclear. If strategies can be developed to remove A epitopes, enzymatic conversion could be used to create a universal (group O) donor blood supply.