Autocatalytic processing of recombinant human procathepsin B is a bimolecular process

FEBS Letters

Rozman, Jerica²  Turk, Boris²  Stojan, Jure¹  Kuhelj, Robert²  Turk, Vito² 

[1]Institute of Biochemistry, Medical Faculty, University of Ljubljana, Vrazov trg 2, 1000 Ljubljana, Slovenia

[2]Department of Biochemistry and Molecular Biology, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia

关键词: Procathepsin B;    Processing;    Autoactivation;   

DOI  :  10.1016/S0014-5793(99)01302-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Cathepsin B and other lysosomal cysteine proteinases are synthesized as inactive zymogens, which are converted to their mature forms by other proteases or by autocatalytic processing. Procathepsin B autoactivation was shown in vitro at pH 4.5 to be a bimolecular process with K _s and k _cat values of 2.1±0.9 μM and 0.12±0.02 s⁻¹, respectively. Autoactivation is substantially accelerated in the presence of active cathepsin B molecules, indicating that mature cathepsin B is the catalytic species in the process. Proenzyme is cleaved without significant conformational changes as judged by circular dichroism, suggesting that propeptide unfolding occurs only after the cleavage. Procathepsin B autoactivation is pH-dependent with a pH optimum at 4.5 and with no processing observed at pH>6.0. However, in the presence of 0.5 μg/ml of dextran sulfate, relatively rapid processing is observed even at pH 6.5 (t _1/2∼90 min), suggesting that glycosaminoglycans are involved in in vivo processing of lysosomal cysteine proteases.

【 授权许可】

Unknown