title: Purification and properties of a thiol protease from rat liver nuclei.
abstract: A thiol protease was purified about 800-fold from the chromatin fraction of rat liver by employing Sepharose 6B gel filtration, chromatofocusing and Sephadex G-100 gel filtration. It was nearly homogeneous on sodium dodecyl sulfate/polyacrylamide gel electrophoresis and its molecular weight was about 29000. The isoelectric point of the enzyme was 7.1. The pH optimum for degradation of 3H-labelled ribosomal proteins was 4.5. It is noticeable that the maximal activity was shifted to pH 5.5 by DNA, and that 30-40% of the maximal activity was observed at neutral pH in the presence of DNA. The activity was increased about twice by 2-4 mM dithiothreitol. The protease may be specific for the nuclei because it is different from all lysosomal thiol proteases ever known.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D055598:Chemical Phenomena; D002621:Chemistry; D002843:Chromatin / Q000302:isolation & purification; D002850:Chromatography, Gel; D003546:Cysteine Endopeptidases; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000302:isolation & purification*; D008099:Liver / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002843:Chromatin; D010450:Endopeptidases; D003546:Cysteine Endopeptidases