Seasonal variations in the properties of rabbit-liver fructose 1 ,6-bisphosphatase have now been linked to corresponding changes in the levels of proteolytic activity in the liver extracts. Incubation of native fructose 1,6-bisphosphatase with purified liver lysosomes causes a 3-fold increase in catalytic activity at pH 9.2, with a smaller, and variable, decrease in activity tested at pH 7. (7), and the mitochondrial fraction was carefully layered on top of a linear 45-60% sucrose gradient containing 1 mM EDTA. The purified lysosome and mitochondria-enriched fractions, respectively, were pooled, diluted to a final sucrose concentration of 0.35 M, and recovered by centrifugation at 10,000 X g. Rabbit liver lysosomes were used in the experiments reported here, but identical results were obtained with lysosomal preparations from mouse liver.Proteolytic activities of crude liver extracts were assayed with bovine-serum albumin as the substrate, by measurement of the amount of ninhydrin-positive material in the supernatant solution after precipitation with trichloroacetic acid. RESULTSEffect of the lysosome fraction on "neutral" FbPase When purified intact lysosomes were incubated at pH 6.5 with native FbPase the enzyme showed a rapid increase in of purified "neutral" FbPase, and 4 mg of lysosomal fraction, in a total volume of 1.0 ml. Aliquots (0.2 ml) were removed as indicated and analyzed for catalytic activity at pH 7.5 and 9.2 (1), and for mobility in Na dodecyl sulfate-polyacrylamide gel electrophoresis. The patterns obtained at various times are illustrated in the lower part of the figure. 303 pH 9.2

No abstract

No abstract