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Updated: Jul 14, 2026
12:11
Simultaneous Affinity Enrichment of Two Post-Translational Modifications for Quantification and Site Localization
Published on: February 27, 2020
Mechanistic and structural analysis of human spermidine/spermine N1-acetyltransferase
Subray S Hegde1, Jonathan Chandler, Matthew W Vetting
1Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA.
Biochemistry
|May 23, 2007
Summary
Spermidine/spermine acetyltransferase (SSAT) regulates cellular polyamines, crucial for health and disease. This study reveals SSAT
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Cellular polyamine levels are critical in eukaryotic cells.
- Dysregulated polyamine levels are linked to various cancers and diseases.
- Spermidine/spermine acetyltransferase (SSAT) is a key enzyme in polyamine metabolism and a potential therapeutic target.
Purpose of the Study:
- To elucidate the kinetic and chemical mechanism of human SSAT.
- To determine the three-dimensional crystal structure of SSAT in complex with a bisubstrate inhibitor.
- To propose a catalytic mechanism for SSAT.
Main Methods:
- Expression and purification of human SSAT in Escherichia coli.
- Kinetic studies including initial velocity and inhibition assays.
- Determination of the crystal structure of the SSAT-spermine-acetyl-coenzyme A complex at 2.3 Å resolution.
- Analysis of pH-activity profile.
Main Results:
- SSAT follows a random sequential catalytic mechanism.
- A bisubstrate analogue showed potent competitive inhibition (Ki = 6 nM).
- The pH-activity profile indicated two critical ionizable groups with pKa values of 7.27 and 8.87.
- Structural analysis revealed Tyr140 and Glu92 as potential catalytic residues involved in acid/base catalysis.
Conclusions:
- SSAT catalyzes its reaction via an acid/base-assisted mechanism involving a ternary complex.
- Understanding SSAT's mechanism provides insights for developing targeted therapies for diseases associated with polyamine dysregulation.
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