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Three β-N-acetylglucosaminidases, GlcNAcase A, B, and C, were purified from the culture fluid of Lactobacillus casei ATCC 27092, and the molecular weights of these enzymes were estimated to be 54,000, 51,000, and 44,000, respectively, by SDS-PAGE. The production of these GlcNAcases was accelerated by the addition of N-acetylglucosamine to the culture. These enzymes had pIs of about 5.2, an optimum pH of 5.0-5.5, and an optimum temperature of 37-40°C. The K m values of GlcNAcase A, B, and C for p-nitrophenyl-β-N-acetylglucosamine were 0.85, 1.30, and 1.04 mM and those for p-nitrophenyl-β-N-acetylgalactosamine were 39.6, 57.7, and 60.8 mM, respectively.

Superoxide dismutase (SOD) is an enzyme facilitating the removal of superoxide anions from living organisms. This study focused on SOD from the silkworm, Bombyx mori (bmSOD). cDNA encoding bmSOD was amplified by reverse transcriptase-polymerase chain reaction. The deduced amino acid sequence of bmSOD indicated that the residues forming the Cu/Zn binding site are conserved and that the sequence is in 60% identity to that of the Drosophila melanogaster. B. mori SOD was also close to the D. melanogaster SOD in a phylogenetic tree. The bmSOD mRNA and the enzyme activity were widely distributed in diverse tissues. bmSOD functionally overexpressed in Escherichia coli in a soluble form was purified, and its stability was examined. bmSOD at 4 degrees C retained almost all of its original activity after incubation at pH 4-11 for 24 h. Incubation (pH 7) for 30 min at temperatures below 40 degrees C also affected activity insignificantly.

We compared the use of wet and dry two-dimensional electrophoresis (2-DE) gels for in-gel tryptic digestion and subsequent analysis by mass spectrometry, first using bovine serum albumin (BSA) as a model protein and then using unknown proteins from an extract of the silkworm midgut. The gel was either dried at 80 degrees C or left wet. Upon analysis of BSA, there was little difference in peptide recovery from 2-DE or in mass spectrum between the dry and the wet gels. The midgut extract was resolved into more than 1,100 protein spots by 2-DE, and 40 of these spots were sampled for further analysis. For all of the 40 proteins, the results obtained from dry and wet gels were quite similar in mass spectra and protein identification, although the relative amounts of peptides from tryptic digestion ranged from 45 to 146%. Based on these results, we confirmed the utility of dry electrophoretic gels for proteomics of insect extracts.