Mammalian STT3A/B oligosaccharyltransferases segregate N-glycosylation at the translocon from lipid-linked oligosaccharide hydrolysis

Oligosaccharyltransferases (OSTs) N-glycosylate proteins by transferring oligosaccharides from lipid-linked oligosaccharides (LLOs) to asparaginyl residues of Asn-Xaa-Ser/Thr acceptor sequons. Mammals have OST isoforms with STT3A or STT3B catalytic subunits for cotranslational or posttranslational N-glycosylation, respectively. OSTs also hydrolyze LLOs, forming free oligosaccharides (fOSs). It has been unclear whether hydrolysis is due to one or both OSTs, segregated from N-glycosylation, and/or regulated. Transfer and hydrolysis were assayed in permeabilized HEK293 kidney and Huh7.5.1 liver cells lacking STT3A or STT3B. Transfer by both STT3A-OST and STT3B-OST with synthetic acceptors was robust. LLO hydrolysis by STT3B-OST was readily detected and surprisingly modulated: Without acceptors, STT3B-OST hydrolyzed Glc3Man9GlcNAc2-LLO but not Man9GlcNAc2-LLO, yet it hydrolyzed both LLOs with acceptors present. In contrast, LLO hydrolysis by STT3A-OST was negligible. STT3A-OST however may be regulatory, because it suppressed STT3B-OST–dependent fOSs. TREX1, a negative innate immunity factor that diminishes immunogenic fOSs derived from LLOs, acted through STT3B-OST as well. In summary, only STT3B-OST hydrolyzes LLOs, depending upon LLO quality and acceptor site occupancy. TREX1 and STT3A suppress STT3B-OST–dependent fOSs. Without strict kinetic limitations during posttranslational N-glycosylation, STT3B-OST can thus moonlight for LLO hydrolysis. In contrast, the STT3A-OST/translocon complex preserves LLOs for temporally fastidious cotranslational N-glycosylation.

THE PRELIMINARY STUDY OF ANTIOXIDANT ACTIVITY FROM XYLO-OLIGOSACCHARIDE OF CORNCOB (ZEA MAYS) HYDROLYSIS PRODUCT WITH ENDO-β-XYLANASE ENZYME

Xylo-oligosaccharide derived from corncob hemicellulose has been reported to possess antioxidant activity. In order to assess the effective scavenging of xylo-oligosaccharide, we conducted in vitro studies based on self-made xylo-oligosaccharide with DPPH (2,2diphenyl-1-picrilhydrazil) method. Xylo-oligosaccharide was prepared with enzymatic hydrolysis. The enzyme used for hemicellulose hydrolysis was endo-β-xylanase enzyme from PC-01 isolated bactrerium. PC-01 isolated bacterium used in this study was Pacet hot spring which was isolated from East Java. Endo-β-xylanase enzyme is an extracelluler enzyme. There was about 0.199 U/mL after purification and dialysis process. Hydrolisis product of hemicellulose A and B from corncob were analyzed with TLC (Thin Layer Chromatography) and HPLC (High Performance Liquid Chromatography). This analysis showed that hydrolysis product of hemicellulose B had a lot of xylo-oligosaccharide hydrolysis product of hemicellulose than Xylo-oligosaccharide hydrolysis product of hemicelluloses A. Xylo-olygosaccharide was analyzed as on antioxidant activity. Xylo-oligosaccharide hydrolysis product ofhemicellulose B (IC = 48.96) has higher antioxidant activity than Xylo-oligosaccharide hydrolysis product of hemicellulose A (IC 50 50 = 92.302). The toxicity of xylo-oligosaccharide can be calculated by the value of LC 50 (Lethality concentration). LC of xylooligosaccharide derived from corncob hemicellulose was 400 ppm so that xylo-oligosaccharide has anti tumor activity because xylooligosaccharide has LC 50 < 1000 ppm.

Acid-modified clays as green catalysts for the hydrolysis of hemicellulosic oligosaccharides

Hemicellulosic oligosaccharide hydrolysis over acid clay catalysts.

Arabinoxylan Oligosaccharide Hydrolysis by Family 43 and 51 Glycosidases from Lactobacillus brevis DSM 20054

ABSTRACTDue to their potential prebiotic properties, arabinoxylan-derived oligosaccharides [(A)XOS] are of great interest as functional food and feed ingredients. While the (A)XOS metabolism ofBifidobacteriaceaehas been extensively studied, information regarding lactic acid bacteria (LAB) is still limited in this context. The aim of the present study was to fill this important gap by characterizing candidate (A)XOS hydrolyzing glycoside hydrolases (GHs) identified in the genome ofLactobacillus brevisDSM 20054. Two putative GH family 43 xylosidases (XynB1 and XynB2) and a GH family 43 arabinofuranosidase (Abf3) were heterologously expressed and characterized. While the function of XynB1 remains unclear, XynB2 could efficiently hydrolyze xylooligosaccharides. Abf3 displayed high specific activity for arabinobiose but could not release arabinose from an (A)XOS preparation. However, two previously reported GH 51 arabinofuranosidases fromLb. breviswere able to specifically remove α-1,3-linked arabinofuranosyl residues from arabino-xylooligosaccharides (AXHm3 specificity). These results imply thatLb. brevisis at least genetically equipped with functional enzymes in order to hydrolyze the depolymerization products of (arabino)xylans and arabinans. The distribution of related genes inLactobacillalesgenomes indicates that GH 43 and, especially, GH 51 glycosidase genes are rare among LAB and mainly occur in obligately heterofermentativeLactobacillusspp.,Pediococcusspp., members of theLeuconostoc/Weissellabranch, andEnterococcusspp. Apart from the prebiotic viewpoint, this information also adds new perspectives on the carbohydrate (i.e., pentose-oligomer) metabolism of LAB species involved in the fermentation of hemicellulose-containing substrates.