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Convergence of active center geometries
Biochemistry
|November 15, 1977
Summary
Enzyme active site geometries reveal substrate stereochemistry dictates nicotinamide ring orientation in dehydrogenases. This conserved specificity suggests evolutionary constraints on enzyme catalytic domains.
Area of Science:
- Enzymology
- Structural Biology
- Biochemistry
Background:
- Enzyme active sites are crucial for catalysis, with specific geometries dictating substrate interactions.
- Dehydrogenases and proteases employ distinct catalytic mechanisms and active site architectures.
Purpose of the Study:
- To compare the active center geometries of lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, chymotrypsin, and papain.
- To investigate the stereochemical determinants of substrate binding and catalytic activity in these enzymes.
- To elucidate the evolutionary implications of conserved active site features.
Main Methods:
- Comparative analysis of enzyme active site geometries.
- Examination of substrate-enzyme interactions and intermediate conformations.
- Stereochemical analysis of tetrahedral intermediates.
Main Results:
- Substrate stereochemistry determines nicotinamide ring orientation in dehydrogenases, predetermining A- or B-side specificity.
- Tetrahedral intermediates in chymotrypsin and papain acylation are of opposite stereochemical hand.
- Tetrahedral intermediates in papain and glyceraldehyde-3-phosphate dehydrogenase acylation are of the same stereochemical hand.
Conclusions:
- Conserved protein folds in evolving dehydrogenases necessitate maintained nicotinamide specificity.
- Serine proteases (e.g., chymotrypsin) and cysteine enzymes (e.g., papain, glyceraldehyde-3-phosphate dehydrogenase) exhibit distinct stereochemical preferences in their catalytic mechanisms.