Enzymes capable of hydrolyzing the ␤-glycosidic linkage between oligosaccharides and ceramides in various glycosphingolipids has been found in microorganisms and invertebrates and designated endoglycoceramidase (EC 3.2.1.123) or ceramide glycanase. Here we report the molecular cloning, characterization, and homology modeling of a novel endoglycoceramidase that hydrolyzes oligogalactosylceramides to produce galactooligosaccharides and ceramides. The novel enzyme was purified from a culture supernatant of Rhodococcus equi, and the gene encoding 488 deduced amino acids was cloned using peptide sequences of the purified enzyme. Eight residues essential for the catalytic reaction in microbial and animal endoglycoceramidases were all conserved in the deduced amino acid sequence of the novel enzyme. Homology modeling of the enzyme using endocellulase E1 as a template revealed that the enzyme displays a (␤/␣) 8 barrel structure in which Glu 234 at the end of ␤-strand 4 and Glu 341 at the end of ␤-strand 7 could function as an acid/base catalyst and a nucleophile, respectively. Site-directed mutagenesis of these glutamates resulted in a complete loss of the activity without a change in their CD spectra. The recombinant enzyme hydrolyzed the ␤-galactosidic linkage between oligosaccharides and ceramides of 6-gala series glycosphingolipids that were completely resistant to hydrolysis by the enzymes reported so far. In contrast, the novel enzyme did not hydrolyze ganglio-, globo-, or lacto-series glycosphingolipids. The enzyme is therefore systematically named "oligogalactosyl-N-acylsphingosine 1,1-␤-galactohydrolase" or tentatively designated "endogalactosylceramidase." Glycosphingolipids (GSLs), 2 amphipathic compounds consisting of oligosaccharides and ceramides, are ubiquitous components of the plasma membrane (1). Recently, it was revealed that GSLs are enriched with other sphingolipids and cholesterol to form microdomains on ectoplasmic membranes. These lipid microdomains, known as detergent-insoluble sphingolipid-enriched domains, so-called DIMs or rafts (2), assemble receptors and signaling molecules such as glycosylphosphatidylinositol-anchored proteins, Src family kinases, and G-proteins (3).6-Gala series GSLs possessing the structure R-Gal␤1-6Gal␤1-1ЈCer have been found in the mollusk (Turbo cornutus) (4), the leech (Hirudo nipponia) (5), the earthworm (Pheretima sp.) (6), and some pathogenic cestode parasites (Echinococcus multilocularis (7), Taenia crassiceps (8), Spirometra erinacei (9), and Metroliasthes cotarunix (10). Recently, it was revealed that aureobasidin A-resistant Zygomycetes species synthesized 6-gala series GSLs (tentatively designated CDS, CTS, CTeS, and CPS) instead of inositol phosphorylceramide (11). Because aureobasidin A, a well known and widely used antifungal agent, was found to inhibit the synthesis of inositol phosphorylceramide, the resistance to the agent may stem from the lack of inositol phosphorylceramide in Zygomycetes. Thus, an inhibitor for the synthesis of 6-gala series GSLs see...

ABSTR ACT. Based on sedimentological a nd micropaleontological work on three sediment cores coll ected at about 167° E in the western Ross Sea, Antarctica, and accelerator mass spectrometer 14C ages of organic carbon, we have reconstructed environmental changes in the area during the late Quaternary. Since 38 ka BP a t latest, this area was a m a rine environment with low productivity. A grounded ice sheet advanced and loaded the sediments before about 30-25 ka BP. After 25 ka BP, th e so uth ernmost site (76°46' S) was covered by floating ice (shelf ice ), preventing deposition of coarse terrigenous materials and maintaining a supply of di atom tests a nd organic carbon until 20 ka BP. The northernmost site (74°33' S ) was in a marin e environment with a mod erate productivity influenced by shelf ice/ice sheet after about 20 ka BP. Since about 10 ka BP' a sedimentary environment similar to the present-day one has prevailed over this area.

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In February 2006, intensive seismic survey was carried out in Sagami Bay area, central Japan, during the KY06-01 cruise using R/V Kaiyo of JAMSTEC (Japan Agency for Marine-Earth Science and Technology). This cruise follows the previous KY05-06 cruise survey, in which we conducted single-channel seismic survey in the same area. Used tools are a 18 channel streamer with two 355 in 3 GI guns, and a single-channel streamer with a cluster gun. We obtained 21 profiles with GIguns in the eastern Sagami Bay, 20 profiles with GI-gun in the western Sagami Bay and 20 profiles with cluster gun near Hatsushima cold seep communities in the western Sagami Bay. Very clear acoustic images were captured with different frequencies on the same lines. We present here the seismic profiles obtained during the KY06-01 cruise.