Transition-state analogues of aminoacyl adenylates

Synthesis and properties of aminoacylamido-AMP: chemical optimization for the construction of an N-acyl phosphoramidate linkage

This paper describes the design and synthesis of a new type of aminoacyl-adenylate analogue (aa-AMPN) having an N-acyl phosphoramidate linkage where the oxygen atom of the mixed anhydride bond of aminoacyl-adenylate (aa-AMP) is replaced by an amino group. This new type of aa-AMP analogue is expected to be useful as material for studies on the recognition mechanism of the aminoacylation of tRNA and other biochemical reactions. The condensation of phosphoramidite derivatives of carboxamides with nucleoside derivatives failed, because the activated phosphoramidite derivatives reacted with not only the hydroxyl groups but also another reactive species. An alternative approach was examined by the reaction of 5'-O-phosphoramidite adenosine derivatives with carboxamide derivatives. The TBTr and TSE groups were chosen for protection of the amino group of amino acid amides and the phosphate group, respectively. Detailed studies revealed that the use of 5-(3,5-dinitrophenyl)-1H-tetrazole as an activating catalyst of phosphoramidites resulted in rapid condensation within 10 min to give fully protected aa-AMPN derivatives. No side reaction occurred. Deprotection of these products via a two-step procedure gave aa-AMPN derivatives in good yields. It also turned out that aa-AMPNs thus obtained are stable under both acidic and basic conditions, such as 0.1 M HCl (pH 1.0) and 0.1 M NaOH (pH 13.0).

A synthesis of acylphosphonic acids and of 1-aminoalkylphosphonic acids: the action of pyruvate dehydrogenase and lactate dehydrogenase on acetylphosphonic acid

Acylphosphonic acids, R-CO-PO(OH)2, have been synthesized by the steps [formula: see text] of which the last is new and provides a mild method for de-esterifying acylphosphonic acids. Their reductive amination gives a simple way of making 1-aminoalkylphosphonic acids. Acetylphosphonic acid inhibited NAD+ reduction by pyruvate with the pyruvate dehydrogenases from Escherichia coli and Bacillus stearothermophilus. The inhibition was competitive with pyruvate, with Ki of 6 microM for the E. coli enzyme (pyruvate Km 0.5 mM) and one of 0.4 mM of the B. stearothermophilus enzyme (pyruvate Km 0.1 mM). Acetylphosphonate and its monomethyl ester are substates for pig heart lactate dehydrogenase, with Km values of 15 mM and 10 mM respectively (pyruvate Km 0.05 mM) and specificity constants one thousandth that for pyruvate.

Influence of the aminoacyl-tRNA synthetase inhibitors and the diadenosine-5'-tetraphosphate phosphonate analogues on the catalysis of diadenosyl oligophosphates formation

Well-known aminoacyl-tRNA synthetase (ARSase) inhibitors, namely the analogues of amino acids and aminoacyl adenylates (aminoalkyl- and aminophosphonyl adenylates with Ki congruent to 0.1 microM) as well as the diadenosine 5',5'''-p1,p4-tetraphosphate (Ap4A) phosphonoanalogues, were for the first time used for the Ap4A biosynthesis regulation. Effects of a set of such compounds on lysyl-, phenylalanyl- and alanyl-tRNA synthetases from E. coli, capable of synthesizing Ap4A in the presence of Zn2+ ions and pyrophosphatase, have been studied. The adenylate analogues were found to inhibit the Ap4A and Ap3A formation (I50 congruent to 6 mM). Aminophosphonic and aminophosphonous acids are not involved in Ap3A and Ap4A biosynthesis and inhibited it at high concentrations. The Ap4A phosphoanalogues slightly inhibited the major reactions of ARSases, as well as the biosynthesis of Ap3A and Ap4A, at a concentration of 5 mM.

Ionization states of the complex formed between 2-benzyl-3-phosphonopropionic acid and carboxypeptidase A

The binding to carboxypeptidase A of two phosphonic acid analogues of 2-benzylsuccinate, 2-DL-2-benzyl-3-phosphonopropionic acid (inhibitor I) and 2-DL-2-benzyl-3-(-O-ethylphosphono)propionic acid (inhibitor II) was studied by observing their 31P resonances when free and bound to the enzyme in the range of pH from 5 to 10. The binding of I by co-ordination to the active-site Zn(II) lowered the highest pKa of I from a value of 7.66(+/- 0.10) to a value of 6.71(+/- 0.17). No titration of any protons on II occurred over the pH range studied. The enzyme-bound inhibitor II also did not titrate over the pH range 6.17-7.60. The pH-dependencies of the apparent inhibition constants for I and II were also investigated by using N-(-2-(furanacryloyl)-L-phenylalanyl-L-phenylalanine as substrate. Two enzymic functional groups with pKa values of 5.90(+/- 0.06) and 9.79(+/- 0.14) must be protonated for binding of inhibitor I, and two groups with pKa values of 6.29(+/- 0.10) and 9.19(+/- 0.15) for binding of inhibitor II. Over the pH range from 6.71 to 7.66, inhibitor I binds to the enzyme in a complex of the enzyme in a more protonated form, and the inhibitor in a less protonated form than the predominant unligated forms at this pH. Mock & Tsay [(1986) Biochemistry 25, 2920-2927] made a similar finding for the binding of L-2-(1-carboxy-2-phenylethyl)-4-phenylazophenol over a pH range of nearly 4 units. The true inhibition constant for the dianionic form of inhibitor I (racemic) was calculated to be 54.0(+/- 5.9) nM and that of the trianionic form to be 5.92(+/- 0.65) nM. The true inhibition constant of the fully ionized II (racemic) was calculated to be 79.8(+/- 6.4) nM.

Phosphonic analogues of tyrosine and 3,4-dihydroxyphenylalanine (dopa) influence mushroom tyrosinase activity

A series of phosphonic analogues of tyrosine and 3,4-dihydroxyphenylalanine (dopa) were synthesized in order to study their interaction with mushroom tyrosinase. 1-Amino-2-(3,4-dihydroxyphenyl)ethylphosphonic acid and 1-amino-2-(3,4-dimethoxyphenyl)ethylphosphonic acid turned out to be substrates for mushroom tyrosinase with Km values of 3.3 mM and 9.3 mM respectively. Shortening of the alkyl chain by one methylene group gave amino-(3,4-dihydroxyphenyl)methylphosphonic acid, one of the most powerful known inhibitors of this enzyme. This compound, racemic as well as in its optically active forms, exerts a mixed type of inhibition with an affinity for the enzyme one order of magnitude greater than that of the natural substrate.