Open AccessCathepsin L
Author(s) -
KIRSCHKE Heidrun,
LANGER Jürgen,
WIEDERANDERS Bernd,
ANSORGE Siegfried,
BOHLEY Peter
Publication year - 1977
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1977.tb11393.x
Subject(s) - leupeptin , chemistry , biochemistry , isoelectric focusing , cathepsin , isoelectric point , cathepsin a , cathepsin b , cathepsin h , pepstatin , cathepsin d , cathepsin o , polyacrylamide gel electrophoresis , arylsulfatase a , antipain , sephadex , enzyme , chromatography , protease
1 Cathepsin L was purified from rat liver lysosomes by cell fractionation, osmotic disruption of the lysosomes in the lysosomal mitochondrial pellet, gel filtration of the lysosomal extract and chromatography on CM‐Sephadex. 2 Cathepsin L is a thiol proteinase and exists in several multiple forms visible on the disc electropherogram. By polyacrylamide‐gel electrophoresis in the presence of sodium dodecyl sulphate, its molecular weight was found to be 23000 – 24000. The isoelectric points of the multiple forms of cathepsin L extended from pH 5.8 – 6.1 ascertained by analytical isoelectric focusing. 3 Using various protein substrates, cathepsin L was found to be the most active endopeptidase from rat liver lysosomes acting at pH 6 – 7. In contrast to cathepsin B 1 , its capability of hydrolyzing N‐substituted derivatives of arginine is low and it does not split esters. 4 Greatest activity is obtained close to pH 5.0 with 70 – 90% of maximal activity at pH 4.0 and pH 6.0 and 30–40% at pH 7.0. 5 The enzyme is strongly inhibited by leupeptin and the chloromethyl ketone of tosyl‐lysine. Leupeptin acts as a pseudo‐irreversible inhibitor. 6 The enzyme is stable for several months at slightly acid pH values in the presence of thiol compounds in a deep‐frozen state.