Enzyme kinetics studies reported in the literature showed that human liver Cathepsin L is active only at lysosomal acidic pH values, while biochemical studies in living cells showed that the enzyme works even at neutral pH values (in a condition compatible with the extracellular compartment). Such an apparent ambiguity highlighted the need of analysing in depth the kinetics of ~29-kDa Cathepsin L, which is the form commonly used in experiments. The stability and catalytic activity of this enzyme were investigated at different pH values, reducing and non-reducing environments, presence of copper, iron and zinc ions, and presence of the natural modulator/inhibitor cystatin B. Our experiments showed that ∼29-kDa human liver Cathepsin L is stable and catalytically functional even at neutral pH values and under non-reducing conditions, which simulate the extracellular compartment. Under these conditions, Cathepsin L was also proved to interact with cystatin B, being also modulated by physiological concentrations of Cu++, Fe++ and Zn++. This paper suppose an advance in the comprehension of the catalytic properties of human liver Cathepsin L, its implications in different physiological processes and its potential use within a drug screening programme in which agents acting extracellularly are being considered.

Enzyme kinetics studies on 29-kDa human liver Cathepsin L

Pietra D.;Ricci C.;Bianucci A. M.
2014-01-01

Abstract

Enzyme kinetics studies reported in the literature showed that human liver Cathepsin L is active only at lysosomal acidic pH values, while biochemical studies in living cells showed that the enzyme works even at neutral pH values (in a condition compatible with the extracellular compartment). Such an apparent ambiguity highlighted the need of analysing in depth the kinetics of ~29-kDa Cathepsin L, which is the form commonly used in experiments. The stability and catalytic activity of this enzyme were investigated at different pH values, reducing and non-reducing environments, presence of copper, iron and zinc ions, and presence of the natural modulator/inhibitor cystatin B. Our experiments showed that ∼29-kDa human liver Cathepsin L is stable and catalytically functional even at neutral pH values and under non-reducing conditions, which simulate the extracellular compartment. Under these conditions, Cathepsin L was also proved to interact with cystatin B, being also modulated by physiological concentrations of Cu++, Fe++ and Zn++. This paper suppose an advance in the comprehension of the catalytic properties of human liver Cathepsin L, its implications in different physiological processes and its potential use within a drug screening programme in which agents acting extracellularly are being considered.
2014
Pietra, D.; Borghini, A.; Ricci, C.; Bianucci, A. M.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/1138028
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