Stefin B, the major low molecular weight inhibitor in ovarian carcinoma.
Endogenous cysteine proteinase inhibitors (CPIs) presumably regulate lysosomal cysteine endopeptidases (CPs), such as cathepsins B and L, in vivo. An imbalance between CPs and CPIs in carcinomas, possibly due to impaired inhibition of proteinases, was reported. Ovarian carcinoma contain high levels of Stefin B and about twentyfold less Stefin A compared to normal epithelial tissue. Stefin B was isolated and characterized. We used alkaline treatment, affinity chromatography on Cm-papain Sepharose, followed by gel filtration and ion-exchange chromatography and anti-Stefin B-Sepharose 4B to isolate two major isoforms of Stefin B with pI values 5.9 and 6.5. M(r) of ovarian Stefin B was close to 14,000 as judged by SDS-PAGE and had a blocked N-terminus. It strongly inhibited papain (Ki = 0.11 nM) and cathepsin L (Ki = 0.035 nM), but only moderately cathepsin B (Ki = 130 nM). As these properties are similar to Stefin B from human and bovine origin, as well as to Stefin B from human histiosarcoma, we believe that tumor Stefin B does not differ from normal Stefin B.
Department of Biochemistry, Jozef Stefan Institute, Ljubljana, Slovenia.
L
L
Kastelic
B
B
Turk
N
N
Kopitar-Jerala
A
A
Stolfa
S
S
Rainer
V
V
Turk
T T
TT
Lah
D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D055312:Cystatin A; D055313:Cystatin B; D015891:Cystatins / Q000302:isolation & purification / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism*; D005260:Female; D006801:Humans; D007525:Isoelectric Focusing; D010051:Ovarian Neoplasms
C524994:CSTB protein, human; D055312:Cystatin A; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; C026407:CSTA protein, human; D055313:Cystatin B