Identification and partial purification of an ATP-stimulated alkaline protease in rat liver.

G. N. DeMartino, A. L. Goldberg

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101 Scopus citations


Extracts from rat liver contain a sulfhydryl-dependent endoprotease which degrades [methyl-14C]globin or 125I-hemoglobin to acid-soluble peptides. This enzyme was isolated from the 100,000 x g supernatant of the homogenate. It showed a pH optimum between 7.5 and 9.5 and very little activity below pH 7.0. The enzyme has an apparent molecular weight of 550,000 as determined on Sepharose 6B column chromatography and sucrose density gradient centrifugation. ATP, at physiological concentrations, as well as pyrophosphate, stimulated the protease activity in these partially purified preparations up to 3-fold. Nonionic detergents such as Triton X-100 increased proteolytic activity and the stimulation by ATP. Other nucleotide triphosphates and ADP also increased proteolysis but less effectively than ATP. Sodium phosphate, creatine phosphate, and EDTA had no stimulatory effect.

Original languageEnglish (US)
Pages (from-to)3712-3715
Number of pages4
JournalJournal of Biological Chemistry
Issue number10
StatePublished - May 25 1979

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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