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Effect of heavy metal cations on the activity of cathepsin D (in vitro study)

Alicja Karwowska1, Radosław Łapiński, Marek Gacko

  • 1Department of Hygiene and Epidemiology, Medical University of Bialystok, Poland. alicja.karwowska@umb.edu.pl

Folia Histochemica Et Cytobiologica
|October 9, 2012
PubMed

Insights

Heavy metal cations like mercury (Hg²⁺) inhibit cathepsin D activity in human aorta and serum by damaging lysosomes. Other tested metals did not show this inhibitory effect on cathepsin D function.

Area of Science:

  • Biochemistry
  • Toxicology
  • Human Physiology

Background:

  • Cathepsin D is a key aspartic protease involved in protein degradation.
  • Lysosomes are cellular organelles containing hydrolytic enzymes, including cathepsin D.
  • Heavy metals are environmental toxins with known cellular effects.

Purpose of the Study:

  • To investigate the impact of various heavy metal cations on cathepsin D activity.
  • To determine if specific heavy metals inhibit cathepsin D in human aorta and serum.
  • To elucidate the mechanism of inhibition, focusing on lysosomal integrity.

Main Methods:

  • Assayed cathepsin D activity using hemoglobin as a substrate at pH 3.5.
  • Tested the effects of iron (Fe²⁺), copper (Cu²⁺), zinc (Zn²⁺), cadmium (Cd²⁺), mercury (Hg²⁺), and lead (Pb²⁺) cations at 1 mmol/l.
  • Examined human aorta homogenate and blood serum samples.

Main Results:

  • Only mercury (Hg²⁺) cations significantly inhibited cathepsin D activity.
  • Mercury cations were observed to damage lysosomes.
  • This lysosomal damage by Hg²⁺ led to the release of cathepsin D.

Conclusions:

  • Mercury cations exhibit specific inhibitory effects on cathepsin D activity in human aorta and serum.
  • The inhibitory mechanism involves direct damage to lysosomes, releasing cathepsin D.
  • This finding highlights the specific toxicological impact of mercury on lysosomal enzymes.

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