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Minimal functional unit of lactate dehydrogenase
1Department of Biological Science and Biotechnology, School of Life Science and Engineering, Tsinghua University, Beijing, China.
Journal of Protein Chemistry
|April 1, 1997
Summary
Modified lactate dehydrogenase (H4) enzyme activity suggests a tetrameric structure requires at least two native subunits for function. The di-subunit appears to be the minimal functional unit in this enzyme.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Lactate dehydrogenase (LDH) exists as various isozymes, including heart (H) and muscle (M) forms.
- Understanding the subunit composition and functional requirements of LDH isozymes is crucial for comprehending enzyme kinetics and regulation.
Purpose of the Study:
- To investigate the subunit composition and minimal functional unit of the tetrameric lactate dehydrogenase (LDH) enzyme.
- To determine the enzymatic activity and electrophoretic properties of hybrid LDH isozymes.
Main Methods:
- Chemical modification of heart LDH (H4) using p-chloromercuribenzoate (PCMB) to create inactive H4.
- Hybridization of modified H4 with native muscle LDH (M4) to form hybrid tetramers.
- Isolation and analysis of hybrid LDH isozymes using polyacrylamide gel electrophoresis (PAGE).
- Enzyme activity staining and Coomassie brilliant blue staining for protein visualization.
Main Results:
- Hybridization produced a mixture of LDH tetramers (M4, H'M3, H2'M2, H3'M, H4').
- PAGE analysis revealed three distinct bands, corresponding to hybrid enzymes.
- Isolated hybrid enzymes (H'M3 and H2'M2) exhibited half the specific activity of native muscle LDH (M4).
- Electrophoretic properties of H'M3 and H2'M2 were similar to native HM3 and H2M2, respectively.
Conclusions:
- The tetrameric enzyme with enzymatic activity must contain at least two native subunits.
- The di-subunit (two native subunits) represents the minimal functional unit of the tetrameric lactate dehydrogenase enzyme.