Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a unique scavenger receptor that plays important roles in atherogenesis and has been thought to function as a monomer. Using coimmunoprecipitation studies, we demonstrate that human LOX-1 (hLOX-1) forms constitutive homo-interactions in vivo. Western blot analysis of cell lysates under nonreducing or reducing conditions revealed one clear immunoreactive species corresponding to the size of a putative receptor dimer or a monomer, respectively, consistent with the presence of disulfide-linked hLOX-1 complexes. Site-directed mutagenesis studies indicated that cysteine 140 has a key role in the formation of these disulfide-linked hLOX-1 dimers. Eliminating this intermolecular disulfide bond markedly impairs the recognition of Escherichia coli by hLOX-1. Furthermore, these dimers can act as a "structural unit" to form noncovalently associated oligomers, as demonstrated by a membrane-impermeant crosslinker, which resulted in immunoreactive species corresponding to the sizes of putative tetramers and hexamers. These results provide the first evidence for the existence of hLOX-1 dimers/oligomers.

A newly isolated Zygosaccharomyces rouxii NRRL 27,624 produced D-arabitol as the main metabolic product from glucose. In addition, it also produced ethanol and glycerol. The optimal conditions were temperature 30 degrees C, pH 5.0, 350 rpm, and 5% inoculum. The yeast produced 83.4 +/- 1.1 g D-arabitol from 175 +/- 1.1 g glucose per liter at pH 5.0, 30 degrees C, and 350 rpm in 240 h with a yield of 0.48 g/g glucose. It also produced D-arabitol from fructose, galactose, and mannose. The yeast produced D-arabitol and xylitol from xylose and also from a mixture of xylose and xylulose. Resting yeast cells produced 63.6 +/- 1.9 g D-arabitol from 175 +/- 1.8 g glucose per liter in 210 h at pH 5.0, 30 degrees C and 350 rpm with a yield of 0.36 g/g glucose. The yeast has potential to be used for production of xylitol from glucose via D-arabitol route.

The nucleotide sequence of the Thermus sp. strain T2 DNA coding for a thermostable ␣-galactosidase was determined. The deduced amino acid sequence of the enzyme predicts a polypeptide of 474 amino acids (M r , 53,514). The observed homology between the deduced amino acid sequences of the enzyme and ␣-galactosidase from Thermus brockianus was over 70%. Thermus sp. strain T2 ␣-galactosidase was expressed in its active form in Escherichia coli and purified. Native polyacrylamide gel electrophoresis and gel filtration chromatography data suggest that the enzyme is octameric. The enzyme was most active at 75°C for p-nitrophenyl-␣-Dgalactopyranoside hydrolysis, and it retained 50% of its initial activity after 1 h of incubation at 70°C. The enzyme was extremely stable over a broad range of pH (pH 6 to 13) after treatment at 40°C for 1 h. The enzyme acted on the terminal ␣-galactosyl residue, not on the side chain residue, of the galactomanno-oligosaccharides as well as those of yeasts and Mortierella vinacea ␣-galactosidase I. The enzyme has only one Cys residue in the molecule. para-Chloromercuribenzoic acid completely inhibited the enzyme but did not affect the mutant enzyme which contained Ala instead of Cys, indicating that this Cys residue is not responsible for its catalytic function.␣-Galactosidases (␣-Gals) are known to occur widely in microorganisms, plants, and animals, and some of them have been purified and characterized (5). ␣-Gals catalyze the hydrolysis of 1,6-linked ␣-galactose residues from oligosaccharides and polymeric galactomannans (19,27,28). In the sugar beet industry, ␣-Gals have been used to increase the sucrose yield by eliminating raffinose, which prevents the crystallization of beet sugar (31). Raffinose and stachyose in beans are known to cause flatulence. ␣-Gal has the potential to alleviate these symptoms, for instance, in the treatment of soybean milk (6).We have studied the substrate specificity of ␣-Gals from eukaryotes by using galactomanno-oligosaccharides, such as 6 3 -mono-␣-D-galactopyranosyl-␤-1,4-mannotriose (Gal 3 Man 3 ) and 63 -mono-␣-D-galactopyranosyl-␤-1,4-mannotetraose (Gal 3 Man 4 ). The structures of these galactomanno-oligosaccharides are shown in Fig. 1. Mortierella vinacea ␣-Gal I (11) and yeast ␣-Gals (32) are specific for Gal 3 Man 3, having an ␣-galactosyl residue (designated the terminal ␣-galactosyl residue) attached to the O-to-6 position of the nonreducing end mannose of ␤-1,4-mannotriose. On the other hand, Aspergillus niger 5-16 ␣-Gal (12) and Penicillium purpurogenum ␣-Gal (27) show a preference for Gal 3 Man 4 , having an ␣-galactosyl residue (designated as the side chain ␣-galactosyl residue) attached to the O-to-6 position of the third mannose from the reducing end of ␤-1,4-mannotetraose. The M. vinacea ␣-Gal II (28) acts on both substrates to almost equal extents. These facts indicate that eukaryotic ␣-Gals were classified into three groups based on the substrate specificity of these galactomanno-oligosaccharides.Genes encoding ␣-Gals have been cloned ...