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Human placenta cytidine deaminase: proton-linked enzyme activity and substrate binding
S Vincenzetti1, M Angeletti, G Lupidi
1Dipartimento di Biologia M.C.A, Università di Camerino, Italy.
Biochemistry and Molecular Biology International
|July 1, 1997
Summary
This study investigated human placenta cytidine deaminase (CDA) enzyme activity. We identified key catalytic site requirements, including ionizable groups and zinc atoms, influencing substrate binding and enzyme function.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Human placenta cytidine deaminase (CDA) is an enzyme with critical biological roles.
- Understanding CDA's catalytic mechanism is essential for its therapeutic targeting.
Purpose of the Study:
- To elucidate the catalytic site requirements of human placenta cytidine deaminase (CDA).
- To investigate the influence of pH on substrate binding and catalysis.
- To characterize the role of zinc ions and active site accessibility.
Main Methods:
- Enzyme kinetics studies across a pH range (3.0-11.0).
- Analysis of pH-dependence of kinetic parameters.
- Fluorescence spectroscopy of enzyme and enzyme-inhibitor complexes using quenchers.
Main Results:
- Identified two classes of ionizable groups in the CDA active site.
- Demonstrated the involvement of four zinc atoms per tetramer in enzyme kinetics.
- Characterized substrate/inhibitor-dependent accessibility of tryptophan residues.
Conclusions:
- CDA's catalytic activity is modulated by specific ionizable groups and zinc coordination.
- Active site accessibility is influenced by substrate and inhibitor binding.
- These findings provide insights into CDA enzyme function and inhibition.