Related Experiment Videos
High-affinity Ca(2+) binding inhibits autoactivation of rat trypsinogen
1Department of Physiology, University of California Los Angeles, Los Angeles, California 90095-1662, USA. miklos@hhmi.ucla.edu
Biochemical and Biophysical Research Communications
|August 31, 2000
Summary
Calcium ions regulate trypsinogen activation. Mutations at amino acid 21 in trypsinogen (Tg) affect this regulation, impacting hereditary pancreatitis risk. This study reveals dual Ca(2+) control over zymogen activation.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Hereditary pancreatitis is linked to mutations in human cationic trypsinogen (Tg).
- Amino acid 21 is critical for mammalian Tg function and regulation.
- Calcium ions (Ca2+) play a role in zymogen activation.
Purpose of the Study:
- To investigate the effect of Thr21 mutations (Thr21 --> Asn and Thr21 --> Ile) on Ca(2+) dependence of zymogen activation.
- To understand the role of Ca(2+) in regulating trypsinogen autoactivation.
- To explore the functional significance of amino acid 21 in trypsinogen.
Main Methods:
- Utilized an autolysis-resistant rat trypsinogen (Tg) mutant (Arg117 --> His).
- Assessed basal and Ca(2+)-dependent autoactivation of wild-type and mutant rat Tg.
- Determined Ca(2+) inhibition (IC50) and stimulation (EC50) concentrations.
Main Results:
- Wild-type rat Tg showed basal autoactivation inhibited by micromolar Ca(2+).
- Mutations at Thr21 diminished basal autoactivation and Ca(2+) inhibition.
- Both wild-type and mutant Tg showed Ca(2+) stimulation at millimolar concentrations.
Conclusions:
- Rat trypsinogen exhibits dual Ca(2+) regulation: stabilization in low Ca(2+) and activation in high Ca(2+).
- Mutations at amino acid 21 alter this Ca(2+) regulatory mechanism.
- Understanding Ca(2+) dependence of trypsinogen activation is crucial for pancreatitis research.