Latency of some glycosidases of rat liver lysosomes

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Abstract
The latency of the α-glucosidase activity of intact rat liver lysosomes was studied by using four substrates (glycogen, maltose, p-nitrophenyl, α-glucoside, α-fluoroglucoside) at a range of substrate concentrations. The results indicate that the entire lysosome population is impermeable to glycogen and maltose, but a proportion of lysosomes are permeable to α-fluoroglucoside and a still higher proportion permeable to p-nitrophenyl α-glucoside. Incubation at 37° C in an osmotically protected buffer of of pH 5.0 caused lysosomes to become permeable to previously impermeant substrates and ultimately to release their α-glucosidase into the medium. The latencies of lysosomal β-glucosidase and β-galactosidase were examined by using p-nitrophenyl β-glucoside and β-galactoside as substrates. The results indicate permeability properties to these substrates similar to that to p-nitrophenyl α-glucoside. On incubation in an osmotically protected buffer of pH 5, lysosomes progressively released their β-galactosidase in soluble form, but β-glucosidase remained attached to sedimentable material. Lysosomal β-glucosidase was inhibited by 0.1% Triton X-100; α-glucosidase and β-galactosidase were not inhibited.