The core 3 structure of the O-glycan, GlcNAc␤1-3Gal-NAc␣1-serine/threonine, an important precursor in the biosynthesis of mucin-type glycoproteins, is synthesized by UDP-N-acetylglucosamine:GalNAc-peptide ␤1,3-Nacetylglucosaminyltransferase (␤3Gn-T; core 3 synthase). The core 3 structure is restricted in its occurrence to mucins from specific tissues such as the stomach, small intestine, and colon. A partial sequence encoding a novel member of the human ␤3Gn-T family was found in one of the data bases. We cloned a complementary DNA of this gene and named it ␤3Gn-T6. The putative amino acid sequence of ␤3Gn-T6 retains the ␤3Gn-T motifs and is predicted to comprise a typical type II membrane protein. The soluble form of ␤3Gn-T6 expressed in insect cells showed ␤3Gn-T activity toward GalNAc␣-p-nitrophenyl and GalNAc␣1-serine/threonine. The ␤1,3-linkage between GlcNAc and GalNAc of the enzyme reaction product was confirmed by high performance liquid chromatography and NMR analyses. ␤3Gn-T6 effectively transferred a GlcNAc to the GalNAc residue on MUC1 mucin, resulting in the synthesis of a core 3 structure. Real time PCR analysis revealed that the ␤3Gn-T6 transcript was restricted in its distribution, mainly to the stomach, colon, and small intestine. We concluded that ␤3Gn-T6 is the most logical candidate for the core 3 synthase, which plays an important role in the synthesis of mucin-type O-glycans in digestive organs.

We found a novel human glycosyltransferase gene carrying a hypothetical ␤1,4-glycosyltransferase motif during a BLAST search, and we cloned its full-length open reading frame by using the 5 -rapid amplification of cDNA ends method. It encodes a type II transmembrane protein of 999 amino acids with homology to chondroitin sulfate synthase in its C-terminal region (GenBank TM accession number AB089940). Its putative orthologous gene was also found in mouse (accession number AB114826). The truncated form of the human enzyme was expressed in HEK293T cells as a soluble protein. The recombinant enzyme transferred GalNAc to GlcNAc ␤-benzyl. The product was deduced to be GalNAc␤1-4GlcNAc␤-benzyl based on mass spectrometry and NMR spectroscopy. We renamed the enzyme ␤1,4-N-acetylgalactosaminyltransferase-III (␤4GalNAc-T3). ␤4GalNAc-T3 effectively synthesized N,N -diacetylgalactosediamine, GalNAc␤1-4GlcNAc, at non-reducing termini of various acceptors derived not only from N-glycans but also from O-glycans. Quantitative real time PCR analysis showed that its transcript was highly expressed in stomach, colon, and testis. As some glycohormones contain N,N -diacetylgalactosediamine structures in their N-glycans, we examined the ability of ␤4GalNAc-T3 to synthesize N,N -diacetylgalactosediamine structures in N-glycans on a model protein.When fetal calf fetuin treated with neuraminidase and ␤1,4-galactosidase was utilized as an acceptor protein, ␤4GalNAc-T3 transferred GalNAc to it. Furthermore, the majority of the signal from GalNAc disappeared on treatment with glycopeptidase F. These results suggest that ␤4GalNAc-T3 could transfer GalNAc residues, producing N,N -diacetylgalactosediamine structures at least in Nglycans and probably in both N-and O-glycans.

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The phreatic eruption at Ontake volcano on 27 September 2014, which caused the worst volcanic disaster in the past half-century in Japan, was reconstructed based on observations of the proximal pyroclastic density current (PDC) and fallout deposits. Witness observations were also used to clarify the eruption process. The deposits are divided into three major depositional units (Units A, B, and C) which are characterized by massive, extremely poorly sorted, and multimodal grain-size distribution with 30-50 wt% of fine ash (silt-clay component). The depositional condition was initially dry but eventually changed to wet. Unit A originated from gravity-driven turbulent PDCs in the relatively dry, vent-opening phase. Unit B was then produced mainly by fallout from a vigorous moist plume during vent development. Unit C was derived from wet ash fall in the declining stage. Ballistic ejecta continuously occurred during vent opening and development. As observed in the finest population of the grain-size distribution, aggregate particles were formed throughout the eruption, and the effect of water in the plume on the aggregation increased with time and distance. Based on the deposit thickness, duration, and grain-size data, and by applying a scaling analysis using a depth-averaged model of turbulent gravity currents, the particle concentration and initial flow speed of the PDC at the summit area were estimated as 2 × 10 −4-2 × 10 −3 and 24-28 m/s, respectively. The tephra thinning trend in the proximal area shows a steeper slope than in similar-sized magmatic eruptions, indicating a large tephra volume deposited over a short distance owing to the wet dispersal conditions. The Ontake eruption provided an opportunity to examine the deposits from a phreatic eruption with a complex eruption sequence that reflects the effect of external water on the eruption dynamics.

We found, using a BLAST search, a novel human gene (GenBank TM accession number BC029564) that possesses ␤3-glycosyltransferase motifs. The full-length open reading frame consists of 500 amino acids and encodes a typical type II membrane protein. This enzyme has a domain containing ␤1,3-glycosyltransferase motifs, which are widely conserved in the ␤1,3-galactosyltransferase and ␤1,3-N-acetylglucosaminyltransferase families. The putative catalytic domain was expressed in human embryonic kidney 293T cells as a soluble protein. Its N-acetylgalactosaminyltransferase activity was observed when N-acetylglucosamine (GlcNAc) ␤1-O-benzyl was used as an acceptor substrate. The enzyme product was determined to have a ␤1,3-linkage by NMR spectroscopic analysis, and was therefore named ␤1,3-Nacetylgalactosaminyltransferase-II (␤3GalNAc-T2). The acceptor substrate specificity of ␤3GalNAc-T2 was examined using various oligosaccharide substrates. Gal-␤1-3(GlcNAc␤1-6)GalNAc␣1-O-para-nitrophenyl (core 2-pNP) was the best acceptor substrate for ␤3GalNAc-T2, followed by GlcNAc␤1-4GlcNAc␤1-O-benzyl, and GlcNAc␤1-6GalNAc␣1-O-para-nitrophenyl (core 6-pNP), among the tested oligosaccharide substrates. Quantitative real time PCR analysis revealed that the ␤3Gal-NAc-T2 transcripts was restricted in its distribution mainly to the testis, adipose tissue, skeletal muscle, and ovary. Its putative orthologous gene, m␤3GalNAc-T2, was also found in a data base of mouse expressed sequence tags. In situ hybridization analysis with mouse testis showed that the transcripts are expressed in germ line cells. ␤3GalNAc-T2 efficiently transferred GalNAc to N-glycans of fetal calf fetuin, which was treated with neuraminidase and ␤-galactosidase. However, it showed no activity toward any glycolipid examined. Although the GalNAc␤1-3GlcNAc␤1-R structure has not been reported in humans or other mammals, we have discovered a novel human glycosyltransferase producing this structure on N-and O-glycans.