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Trehalase transformation in silkworm mid gut during metamorphosis

Journal of Comparative Physiology B Metabolic and Transport Functions 115(2): 241-253
Trehalase transformation in silkworm mid gut during metamorphosis
The particulate trehalase from silkworm [Bombyx mori] larval midgut was effectively solubilized by repeated freezing and thawing, and by incubation with snake venom and non-ionic detergents (Lubrol PX and WX and Triton X-100). With solubilization the activity was enhanced and the activation behavior was dependent upon the developmental stage of silkworms, being highest (up to .apprx. 3-fold) at the spinning stage. When chromatographed on DEAE-cellulose columns separately, the enzyme solubilized by freezing and thawing and the soluble trehalases from feeding larval midgut were eluted as single peaks, P I and P II, respectively. P I and P II trehalases were demonstrated after solubilization of the particulate fraction from feeding larvae with Triton X-100, or after treatment of the midgut of spinning larvae by freezing and thawing. The apparent MW of P I and P II trehalases, an estimated by Sephadex G-200 chromatography, were .apprx. 70,000 and 140,000, respectively. The optimum pH was 6.0 for P I and .apprx. 5.0 for P II trehalase. The Km values were .apprx. 1.0 mM for P I trehalase and 0.30 mM for P II trehalase. In feeding larval midgut there are 2 types of trehalase distinguishable from each other by intracellular localization, protein nature and kinetic properties. When the midgut undergoes metamorphosis, the P I enzyme found predominantly in feeding stages seems to transform to the P II enzyme via an intermediate form (Ppt-P II) with transitional properties.

Accession: 006839070

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