Plant P5C Reductase as a New Target for Aminomethylenebisphosphonates

Abstract

A series of N-substituted derivatives of aminomethylenebisphosphonic acid were evaluated as potential inhibitors of delta1-pyrroline-5-carboxylate reductase (EC 1.5.1.2), the enzyme that catalyzes the last step in proline biosynthesis, partially purified from Arabidopsis thaliana suspension cultured cells. At millimolar concentrations, three compounds out of 26 were found to interfere with the catalytic mechanism. One of them, namely, 3,5-dichloropyridyl-aminomethylenebisphosphonic acid, retained such inhibitory activity in the micromolar range. Kinetic analyses ruled out the possibility that the inhibition could simply rely upon the chelating properties of bisphosphonates and showed mechanisms of a noncompetitive type against NADH and an uncompetitive type against delta1-pyrroline-5-carboxylic acid, with KI values of 199 +/- 6 and 10.3 +/- 1.5 microM, respectively. A computer-aided docking analysis, performed on the basis of the crystal structure of the enzyme from Streptococcus pyogenes, suggested that this phosphonate may interact with amino acid residues near the binding site of delta1-pyrroline-5-carboxylic acid, thus blocking the substrate in a pocket and preventing its interaction with NADH. Because in higher plants the step catalyzed by delta1-pyrroline-5-carboxylate reductase is shared by all pathways leading to proline synthesis, such a compound may represent a lead structure to be exploited for the design of new substances endowed with herbicidal activity.

Physiologic Activity of Bisphosphonates – Recent Advances

“…This inhibitory activity was observed when studying bleaching herbicides influencing biosynthesis of caretonoids. Further studies have shown that herbicidal aminomethylene-bisphosphonates may be considered multi-target substances, which was documented by their inhibitory activities towards glutamine synthetase, [198,199] 3-deoxy-D-arabinoheptulosonate-7-phosphate (DAHP) synthase, [200] δ 1 -pyrroline-5-carboxylate (P5CR) reductase [201,202] and pyrophosphatase [203]. Thus, these compounds may be considered a heterogeneous group of compounds with variable modes of action (Scheme 11).…”

δ1-Pyrroline-5-carboxylate reductase as a new target for therapeutics: inhibition of the enzyme from Streptococcus pyogenes and effects in vivo

“…Since this dual anabolic route is shared also by plants (Lehmann et al 2010), P5C reductase inhibitors might find application in crop protection as well. We previously synthesized and screened several derivatives of aminomethylenebisphosphonic acid (compound 01) for the ability to inhibit plant P5C reductase (Forlani et al 2007). A group of phenyl derivatives were found effective in the micromolar to millimolar range, and indeed showed phytotoxic properties (Forlani et al 2008a).…”

Coenzyme preference of Streptococcus pyogenes δ1-pyrroline-5-carboxylate reductase: evidence supporting NADPH as the physiological electron donor

“…Some phosphonate inhibitors were indeed found to exert both phytotoxic (Forlani et al 2007(Forlani et al , 2008 and antibiotic (Forlani et al 2011) effects. Here we report the results of a thorough biochemical characterization of P5CR from S. pyogenes, shedding more light on its substrate preference and reaction mechanism.…”