Properties of the phosphonomethyl isosteres of two phosphate ester glycolytic intermediates

Gram scale synthesis of 3-fluoro-1-hydroxyacetone phosphate: a novel donor substrate in rabbit muscle aldolase-catalyzed aldol reactions

An efficient gram scale synthesis of 3-fluoro-1-hydroxyacetone phosphate (FHAP) has been developed. As a close analog to dihydroxyacetone phosphate, FHAP was used as a novel donor substrate for rabbit muscle aldolase catalyzed reactions. The different binding affinities of the gem-diol and keto form of FHAP were studied by (19)F-NMR.

Synthesis of phosphono analogues of dihydroxyacetone phosphate and glyceraldehyde 3-phosphate

The present paper describes the synthetic routes of six phosphono analogues of dihydroxyacetone phosphate and five phosphono analogues of glyceraldehyde 3-phosphate through alpha-, beta- and gamma-hydroxyphosphonate esters precursors containing a protected carbonyl group. In some situations, depending on the sequence used for the deprotection of the phosphonate and carbonyl groups, the aldol/ketol rearrangement allowed the synthesis of either dihydroxyacetone phosphate or glyceraldehyde 3-phosphate analogues from the same precursors. All these analogues are of interest both as active-site probes and as potential substrates for glycolytic enzymes such as fructose 1,6-diphosphate aldolases (EC 4.1.2.13).

Interaction of phosphonomethyl analog of dihydroxyacetone phosphate with rabbit muscle aldolase

Aldolase presents the same binding affinity for dihydroxyacetone phosphate and its phosphonomethyl analog, but the partition coefficient between the intermediates from the Michaelis complex to the eneamine is different. The effects of the structural modification of the triose phosphate substrate on the interaction with rabbit muscle aldolase are discussed in connection with the mechanistic pathway and the three-dimensional structure of the enzyme.

Practical synthesis of 4-hydroxy-3-oxobutylphosphonic acid and its evaluation as a bio-isosteric substrate of DHAP aldolase

An efficient four step synthesis of the title compound 4-hydroxy-3-oxobutylphosphonate (2) has been developed based on inexpensive 4-ethoxy-1-hydroxybutane-2-one using an Arbusow reaction (59% overall yield). Several dihydroxyacetone-dependent aldolases having different stereospecificities were tested for their acceptance of this phosphonomethyl substrate mimic as the aldol donor. Individual enzymes belonging to both type I (Schiff base formation) and type II (Zn2+ catalysis) mechanistic classes were found to catalyze the stereoselective addition of 2 to simple aldehydes to provide bio-isosteric analogs of sugar 1-phosphates in high yields. The lack of acceptance by specific enzymes is discussed with regard to recent protein X-ray data.

Arsenite release on enzymic transformation of arsonomethyl substrate analogues: a potentially lethal synthesis by glycerol-3-phosphate dehydrogenase

The isosteric arsenical analogue of glycerol 3-phosphate, 3,4-dihydroxybutylarsonic acid, is a good substrate for rabbit muscle glycerol-3-phosphate dehydrogenase. Its oxidation is accompanied by release of arsenite. This release seems to be due to a spontaneous elimination of arsenite by 3-oxoalkylarsonic acids, as it is also observed in (1) the oxidation of 3-hydroxypropylarsonic acid by yeast alcohol dehydrogenase, (2) treatment of 3,4-dihydroxybutylarsonic acid with periodate and (3) nonenzymic transamination of the glutamate analogue 2-amino-4-arsonobutyric acid. Enzymic formation of 3-oxoalkylarsonic acids in cells can therefore be lethal, as arsenite is poisonous to most organisms because of its high affinity for dithiols such as dihydrolipoyl groups.

Inhibition of the photosynthetic activities of isolated spinach chloroplasts by phosphonate compounds

The effects of three closely related phosphonate compounds on several photosynthetic activities of isolated chloroplasts were investigated. Phosphonoformic and phosphonopropionic acid were found to inhibit both CO(2) fixation and the reduction of 3-phosphoglyceric acid, with CO(2) fixation being more sensitive. In contrast, phosphonoacetic acid was only slightly inhibitory. The lack of inhibition appeared to be due to its inability to enter the stroma via the phosphate translocator. Measurements of changes in stromal metabolite levels following the inhibition of CO(2) fixation by either phosphonoformic or phosphonopropionic acid indicated that the activity of ribulose bisphosphate carboxylase/oxygenase was reduced. Studies with the isolated enzyme confirmed that both of these compounds were effective competitive inhibitors of the carboxylase activity of the enzyme.

The phosphonomethyl analogue of 3-phosphoglycerate is a potent competitive inhibitor of phosphoglycerate mutases

The phosphonomethyl analogue of 3-phosphoglycerate (2-hydroxy-4-phosphonobutanoate) is a potent competitive inhibitor of cofactor-dependent phosphoglycerate mutase from yeast and of cofactor-independent phosphoglycerate mutase from wheat germ. For the yeast enzyme Ki is 1.3 mM (Km for substrate is 0.71 mM); for the wheatgerm enzyme Ki is 18 mM (Km for substrate is 0.86 mM). This analogue should be a useful tool for n.m.r. spectroscopic studies on the mechanism of action of the two mutases. The arsonomethyl analogue of 3-phosphoglycerate (4-arsono-2-hydroxybutanoate) was a relatively poor inhibitor.

Dehydrogenation by gluconate 6-phosphate dehydrogenase of an isosteric phosphonate substrate analogue

6,7-Dideoxy-D-gluco-heptonic-7-phosphonic acid, the isosteric phosphonate analogue of gluconate 6-phosphate, was prepared by incubation of the corresponding analogue of glucose 6-phosphate with glucose 6-phosphate dehydrogenase and NADP+ in the presence of an enzyme NADPH-NADP+ recycling system. The analogue of gluconate 6-phosphate is a substrate for yeast gluconate 6-phosphate dehydrogenase, showing Michaelis-Menten kinetics at pH 7.5 and 8.0. At both pH values the Km values are approx. 3-fold higher and the Vmax. values approx. 7-fold lower than those of the natural substrate.

The biological importance of organophosphorus compounds containing a carbon-phosphorus bond

Organophosphorus anticholinesterase compounds may be derivatives of phosphoric acid or of a phosphonic acid. The phosphonic acid derivatives are usually more reactive and more toxic than the phosphoric acid derivatives. Examples are given to show that differences in the chemical and biological reactivity of phosphates and phosphonates reflect many different aspects of their chemical structure. Some recently discovered naturally-occurring phosphonates are described, together with some synthetic phosphonate analogues of naturally-occurring phosphates. The utility of these synthetic phosphonates as tools for probing enzymic reaction sequences is discussed.

Phosphonomethyl analogues of hexose phosphates

The analogue of fructose 1,6-bisphosphate in which the phosphate group, -O-PO3H2, on C-6 is replaced by the phosphonomethyl group, -CH2-PO3H2, was made enzymically from the corresponding analogue of 3-phosphoglycerate. It was a substrate for aldolase, which was used to form it, but not for fructose 1,6-bisphosphatase. It was hydrolysed chemically to yield the corresponding analogue of fructose 6-phosphate [i.e. 6-deoxy-6-(phosphonomethyl)-D-fructose, or, more strictly, 6,7-dideoxy-7-phosphono-D-arabino-2-heptulose]. This proved to be a substrate for the sequential actions of glucose 6-phosphate isomerase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Thus seven out of the nine enzymes of the glycolytic and pentose phosphate pathways so far tested catalyse the reactions of the phosphonomethyl isosteres of their substrates.

Dehydrogenation of the phosphonate analogue of glucose 6-phosphate by glucose 6-phosphate dehydrogenase

6,7 -Dideoxy-alpha-D-gluco-heptose 7-phosphonic acid, the isosteric phosphonate analogue of glucose 6-phosphate, was synthesized in six steps from the readily available precursor benzyl 4,6-O-benzylidene-alpha-D-glucopyranoside. The analogue is a substrate for yeast glucose 6-phosphate dehydrogenase, showing Michaelis-Menten kinetics at pH7.5 and 8.0. At both pH values the Km values of the analogue are 4-5 fold higher and the values approx. 50% lower than those of the natural substrate. The product of enzymic dehydrogenation of the phosphonate analogue at pH8.5 is itself a substrate for gluconate 6-phosphate dehydrogenase.

Dehydration of a phosphonate substrate analogue by glycerol 3-phosphate dehydrogenase

S-(+)-3,4-Dihydroxybutylphosphonic acid, an isosteric analogue of sn-glycerol 3-phosphate, was synthesized stereospecifically and shown to be an effective substrate for rabbit muscle glycerol 3-phosphate dehydrogenase (sn-glycerol 3-phosphate-NAD(+) oxidoreductase, EC 1.1.1.8). Non-isosteric phosphonate analogues of sn-glycerol 3-phosphate showed neither substrate nor inhibitory activity with the enzyme.

The interaction of the phosphonate analogue of 3-phospho-D-glycerate with phosphoglycerate kinase

The methylene analogue of 3-phospho-d-glycerate, 2-hydroxy-4-phosphono-dl-butyric acid, is a substrate for phosphoglycerate kinase. The pK(a) values for the final dissociation of the natural substrate and its methylene isostere are 6.20 and 7.45 respectively. The kinetic parameters K(m) and k(cat.) for the enzyme-catalysed reaction were determined at pH6.9 and 8.5 by using low substrate concentrations. Although the k(cat.) values for the two substrates at each pH are similar, there is a 60-fold increase in the K(m) value for the methylene isostere on going to the lower pH. The results are most readily interpreted in terms of a dianionic group on C-3 being required for efficient substrate binding to the enzyme.

Phosphonomethyl analogues of phosphate ester glycolytic intermediates

Analogues of dihydroxyacetone phosphate and of 3-phosphoglycerate were made in which the phosphate group, -O-PO(3)H(2), is replaced by the phosphonomethyl group, -CH(2)-PO(3)H(2). The analogue of dihydroxyacetone phosphate is a substrate for aldolase and glycerol 1-phosphate dehydrogenase (Stribling, 1974), but not for triose phosphate isomerase. The analogue of 3-phosphoglycerate oxidizes NADH under the combined action of 3-phosphoglycerate kinase and glyceraldehyde 3-phosphate dehydrogenase if ATP is added. Thus four out of the five glycolytic enzymes tested handle the phosphonomethyl compounds like the natural phosphates.