Site of secretion and properties of endogenous endo-β-1,4-glucanase components from Reticulitermes speratus (Kolbe), a Japanese subterranean termite (original) (raw)

Two endo-/3-1,4-glucanase components (YEGI and YEG2) of the endogenous cellulase from the Japanese subterranean termite, Reticulitermes speratus, were purified to homogeneity using gel filtration and hydroxylapatite chromatography, and their enzymatic properties were investigated. Using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), YEGI and YEG2 had Mr of 42 kDa and 41 kDa, respectively. Both components had an optimal pH of 6.0, an optimal temperature of 50°C and were stable at 40°C fop at least 30 min. Both components showed high activity on sodium carboxymethylcelluiose (CMC), 73.6 U/mg protein for YEGI and 83.4 U/mg protein for YEG2. The Km values of YEGI and YEG2 on CMC were 1.83 mg/ml and 1.48 mg/ml, respectively. YEGI did not hydrolyse cellotetraose or ceHotriose, whereas YEG2 hydrolysed cellotetraose to ceUobiose and cellotriose to cellobiose and glucose. Both YEGI and YEG2 hydrolysed cellopentaose to cellotriose and cellobiose. Neither component hydrolysed cellobiose. The hydrolytic products from crystalline cellulose (Sigmacell type 20) by YEGI and YEG2 were cellobiose and a trace amount of glucose. Polyclonal mouse anti-serum raised against YEG2 crossreacted with YEGI, suggesting a common origin for both components. Using this anti-serum, Western blotting and immunohistochemistry showed the presence of YEGI and YEG2 in the salivary glands, but not in the midgut epithelium. The data suggest that the salivary glands are the site of secretion of endo-~-l,4glucanase in R. speratus.