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. 2013;8(2):e56957.
doi: 10.1371/journal.pone.0056957. Epub 2013 Feb 22.

Identification of a Small Molecule That Selectively Inhibits Mouse PC2 Over Mouse PC1/3: A Computational and Experimental Study

Free PMC article

Identification of a Small Molecule That Selectively Inhibits Mouse PC2 Over Mouse PC1/3: A Computational and Experimental Study

Austin B Yongye et al. PLoS One. .
Free PMC article


The calcium-dependent serine endoproteases prohormone convertase 1/3 (PC1/3) and prohormone convertase 2 (PC2) play important roles in the homeostatic regulation of blood glucose levels, hence implicated in diabetes mellitus. Specifically, the absence of PC2 has been associated with chronic hypoglycemia. Since there is a reasonably good conservation of the catalytic domain between species translation of inhibitory effects is likely. In fact, similar results have been found using both mouse and human recombinant enzymes. Here, we employed computational structure-based approaches to screen 14,400 compounds from the Maybridge small molecule library towards mouse PC2. Our most remarkable finding was the identification of a potent and selective PC2 inhibitor. Kinetic data showed the compound to be an allosteric inhibitor. The compound identified is one of the few reported selective, small-molecule inhibitors of PC2. In addition, this new PC2 inhibitor is structurally different and of smaller size than those reported previously. This is advantageous for future studies where structural analogues can be built upon.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.


Figure 1
Figure 1. The binding surface of a homology model of mouse PC2 along with the top ten poses of the Maybridge database docked to PC2.
In the first image the P1, P2 and P4 subsites with high electronegative potential are depicted in color, while in the subsequent images the surface of the enzyme is color-coded based on the electrostatic potential of the residues.
Figure 2
Figure 2. Distribution of ligands within subsites in the binding pocket of PC2.
(A) Ligands accommodated in distinct subsites; (B) A ligand that spread into the P2 and P4 subsites; (C) Ligands that overlapped with the P1 and P4 sites, which may be used as frameworks to link fragments in the P1, P2 and P4 subsites shown in (A).
Figure 3
Figure 3. A Maybridge ligand that simultaneously occupies the P1, P2 and P4 sites in PC2.
Generic surface plot, with the ligand occupying the three sites (A). The enzyme’s surface is rendered based on electrostatic potential (B). Rank, #55; Average docking score, −9.39; Weight = 517.634 Da.
Figure 4
Figure 4. Distribution of molecular weights for 115 compounds docked utilizing both FRED and GlideXP.
These are the top 115 scoring compounds obtained from docking the Maybridge database to the mouse PC2 models. The compounds are color-coded based on molecular weight. Yellow is the median and represents a molecular weight of 283.31 Da.
Figure 5
Figure 5. Compounds that activated PC2 (HTS05737 and JFD02062) and PC1/3 (BTB03195).
RJC00847 selectively inhibited PC2.
Figure 6
Figure 6. Enzymatic assay of RJC00847 against PC2.
A). The effect of increasing the concentration of the inhibitor on the detection of fluorescent product, 7-amino-4-methylcoumarin (AMC). B). Concentration-response curve, from which an IC50 value of 1.1±0.06 µM was determined.
Figure 7
Figure 7. The active site and potential allosteric sites of PC2, as determined using two structural models of the enzyme.
The first and second numbers in parentheses denote the ranking of each site in model 6 and the homology model, respectively. (See the section Generating structural models of PC2 for ligand docking for details).

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