Peptidase activities of the 20/26S proteasome and a novel protease in human brain.
Many neurodegenerative diseases are characterized by ubiquitin-positive protein aggregates or inclusion bodies. Ubiquitin-conjugated proteins are degraded by the 20/26S proteasome, and reduced proteasome peptidase activities in brain homogenates have been reported in pathologic lesions of Parkinson's and Alzheimer's diseases. However, it is unknown whether crude extracts of human brain contain other proteases having peptidase activities. We found a novel protease of molecular weight of approximately 105 kDa in normal human brain, which exhibited trypsin-like (T-L) and chymotrypsin-like (ChT-L) activities (corresponding to 52% and 21% of the total activities in crude extracts) but not peptidyl glutamyl peptide hydrolase activity. Both T-L and ChT-L activities of this protease were partially inhibited by proteasome inhibitors (MG132, lactacystin) and, in contrast to those of the proteasome, also by sodium dodecyl sulfate. A simple method to obtain a brain fraction specific to the 20/26S proteasome was developed. Our human brain data suggest that T-L and ChT-L activity levels of the proteasome reported previously may include those of the 105 kDa protease, an enzyme of as yet unknown biological significance, and that it is necessary to separate the proteasome from this protease to evaluate the actual status of the ubiquitin-proteasome system in neurodegenerative disorders.
Vigouroux
Sophie
S
Laboratoire de Biochimie Appliquée -UA INRA 995, Université Blaise Pascal, Aubière, France.
Furukawa
Yoshiaki
Y
Farout
Luc
L
J  Kish
Stephen
S
Briand
Marièle
M
Briand
Yves
Y
D000368:Aged; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology*; D001923:Brain Chemistry; D002850:Chromatography, Gel; D003546:Cysteine Endopeptidases / Q000737:chemistry*; D010450:Endopeptidases / Q000737:chemistry* / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000737:chemistry*; D010447:Peptide Hydrolases / Q000737:chemistry*; D011233:Precipitin Tests; D046988:Proteasome Endopeptidase Complex; D012016:Reference Values
D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D010450:Endopeptidases; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease