Kinetic Studies of Newly Patented Aminoalkanol Derivatives with Potential Anticancer Activity as Competitive Inhibitors of Prostate Acid Phosphatase

Abstract

Background: Acid phosphatase and its regulation are important objects of biological and clinical research and play an important role in the development and treatment of prostate and bone diseases. The newly patented aminoalkanol (4-[2-hydroxy-3-(propan-2-ylamino)propyl]-1,7-dimethyl-8,9-diphenyl-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5,10-trione hydrochloride) (I) and (4-[3-(dimethylamino)-2-hydroxypropyl]-1,7-dimethyl-8,9-diphenyl-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5,10-trione hydrochloride) (II) derivatives have potential anticancer activity, and their influence on enzymatic activity can significantly impact the therapeutic effects of acid phosphatase against many diseases. Therefore, in this study, we investigated the action of compounds (I) and (II) on acid phosphatase.

Methods: Capillary electrophoresis was used to evaluate the inhibition of acid phosphatase. Lineweaver-Burk plots were constructed to compare the Km of this enzyme in the presence of inhibitors (I) or (II) with the Km in solutions without these inhibitors.

Results: Compound (I) showed a stronger competitive inhibition against acid phosphatase, whereas derivative (II) showed a weaker competitive type of inhibition. The detailed kinetic studies of these compounds showed that their type and strength of inhibition as well as affinity depend on the kind of substituent occurring in the main chemical molecule.

Conclusions: This study is of great importance because the disclosed inhibition of acid phosphatase by compounds (I) and (II) raises the question of whether these compounds could have any effect on the treatment possibilities of prostate diseases.

Keywords: acid phosphatase inhibitors; anticancer drugs; capillary electrophoresis.

Figure 1

Structures of compounds (I) (4-[2-hydroxy-3-(propan-2-ylamino)propyl]-1,7-dimethyl-8,9-diphenyl-4-azatricyclo [5.2.1.0^2,6] dec-8-ene-3,5,10-trione hydrochloride) and (II) (4-[3-(dimethylamino)-2-hydroxypropyl]-1,7-dimethyl-8,9-diphenyl-4-azatricyclo[5.2.1.0^2,6]dec-8-ene-3,5,10-trione hydrochloride).

Figure 2

Representative electrophoregrams of: (A) 1.44 mM of p-nitrophenyl phosphate (PN-TE) (1) and 0.018 mM of the reaction product p-nitrophenol (PN-OL) (2) in 2 mL of incubation sample; (B) 1.44 mM of PN-TE (1) and 0.018 mM of the reaction product PN-OL (2) in the presence of 0.05 mM of (I) in 2 mL of incubation sample; and (C) 1.44 mM of PN-TE (1) and 0.009 mM of the reaction product PN-OL (2) in the presence of 0.05 mM of (II) in 2 mL of incubation sample.

Figure 3

Michaelis–Menten and Lineweaver–Burk plots for the reaction of acid phosphatase with p-nitrophenyl phosphate inhibited by: (•) 0.00 mM, (•) 0.01 mM, (•) 0.03 mM, (•) 0.04 mM and (•) 0.05 mM (I). The figure shows three straight lines with different intersection points with the 1/S axis and a common intersection with the 1/V axis. Such a system indicates the competitive type of inhibition. The larger the slope of the curve, the stronger the competitive inhibitor of the tested compound is.

Figure 4

Michaelis–Menten and Lineweaver–Burk plots for the reaction of acid phosphatase with p-nitrophenyl phosphate inhibited by: (•) 0.00 mM, (•) 0.01 mM, (•) 0.03 mM, (•) 0.04 mM and (•) 0.05 mM (II). The figure shows three straight lines with different intersection points with the 1/V axis and a common intersection with the 1/S axis. Such a system indicates the competitive type of inhibition. The larger the slope of the curve, the stronger the competitive inhibitor of the tested compound is.

Figure 5

Determination of half-maximal inhibitory concentration (IC₅₀) for compound (I) and (II).

Figure 6

Structure of the active site of prostatic acid phosphatase and potential types of interactions between the competitive inhibitor (I) and (II) and amino acids present in the active site of the enzyme.

Figure 7

Structure and bioactive conformation of the inhibitor in a binding pocket of prostatic acid phosphatase.

Figure 8

Scheme of the reaction catalyzed by acid phosphatase. The reaction rate was determined by the rate of loss of the amount of substrate (p-nitrophenyl phosphate) and the increase in the amount of product (p-nitrophenol) per unit of time.