THE ROLE OF LYSOSOMES IN PROTEIN TURNOVER

摘要: Abstract: A substance has been purified to apparent homogeneity from rat liver which, as previously reported (1), specifically stabilizes the major isozyme of phosphofructokinase (PFK-L2) against thermal inactivation and whose level in vivo changes parallel with precedence that enzyme. Molecular weight determinations gave values around 3,500. Evidence for peptide nature factor includes its correspondence ninhydrin-positive material on gel filtration paper electrophoresis susceptibility pronase. Amino acid analysis yielded only glutamate, glycine, half-cystine, equimolar amounts. However, neither GSH nor GSSG have PFK-L2 stabilizing activity. No free sulfhydryl groups were present. Chemical tryptophan was also negative. The ultraviolet spectrum confirmed absence aromatic amino acids. is unstable storage cold but stabilized by glucose or dithiothreitol. It slowly denatured heat reduced pH even presence glucose. induced fasted animals glucose, nutrients tested, diabetic insulin. Induction both insulin blocked cycloheximide actinomycin. time course induction more rapid two a marked overshoot 3 times normal levels at 12 hours. Increased preceded increased brought about administration. Native inactivated lysosomal extracts, this strongly inhibited factor. These results are accord proposal plays role regulating turnover vivo. In addition, an activator PFK inhibitor fructose-1,6-biphosphatase (2).