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Updated: Oct 13, 2026

High-throughput Identification of Synergistic Drug Combinations by the Overlap2 Method
Published on: May 21, 2018
Multiple sites and synergism in the binding of inhibitors to microsomal aminopeptidase
M DiGregorio1, D S Pickering, W W Chan
1Department of Biochemistry, McMaster University, Hamilton, Ontario, Canada.
Abstract:
The active site of microsomal aminopeptidase has been probed by studying the inhibition of the enzyme in the simultaneous presence of two ligands. The results have been analyzed with the Yonetani-Theorell plot to quantitate the degree of interaction between the two inhibitors. As expected, the enzyme contains a strong binding site for the alpha-amino group and the hydrophobic side chain of specific substrates. In addition, however, the enzyme can interact with another amine and a second hydrophobic group. Evidence suggests that this extra amine may bind to the zinc in an unprotonated form and that one of the hydrophobic sites is located in the vicinity. Another unexpected finding in this work is a strong synergism between the binding of ammonia and that of zinc ligands such as hydroxamates. This synergism may reflect an induced-fit mechanism that brings the catalytically important zinc atom into the optimal state only in the presence of specific substrates.
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