Soybean lipoxygenase-1 inhibition by ketone hydrazones

Abstract

Acetone phenylhydrazone has recently been discovered as a predominant inhibitor of arachidonic acid lipoxygenase in platelets [1]. We found that besides this compound a variety of hydrazones derived from other ketones and hydrazines exhibited similar or more interesting inhibition patterns both against soybean lipoxygenase and rat renal prostaglandin synthetase. Depending on their molecular structure, relatively selective inhibitors of the two arachidonate peroxidation pathways are introduced which may be useful tools for further investigation of the fatty acid oxygenation cascade.

Decreasing Inhibitory Potency of Prostaglandin Synthetase Inhibitors during Their Cooxidative Metabolism

“…Concentration-response curves of all these inhibitors were made and exemplary concentration effects are shown in figure 4. As shown in previous lipoxygenase inhibi tion studies [15,20], AcPh was the most potent inhibitor of lipoxygenase-dependent cooxygenation in comparison with NDHG, 1,5-DHN, phenidone and HgCh. Acetylsalicylic acid and indomethacin lack any antili poxygenase activity.…”

“…Figure 4 shows that the cooxygenation of DIBF trig gered by lipoxygenase in the presence of fatty acid is strictly lipoxygenase-dependent. In contrast to acetylsalicylic acid, which only inhibits PG synthesis, dual inhibitors of ara chidonic peroxidation like phenidone or 1,5-DHN and the more selective lipoxygenase inhibitors AcPh, NDHG and mercuric chlo- ride [15,20] could suppress this type of DIBF cooxygenation in a concentration-dependent manner. Concentration-response curves of all these inhibitors were made and exemplary concentration effects are shown in figure 4.…”

“…Inhibition o f Soybean Lipoxygenase (EC 1.13.11.12) ( l-l4C)-arachidonic acid lipoxygenation was car ried out at 25 °C in a mixture containing 50 mmol/l potassium phosphate buffer (pH 8.0), 1 % ethanol, (1-l4C)-arachidonic acid (37.5 nCi, 2.5 pmol/1), soybean lipoxygenase (750 IU) and inhibitor in a final volume of 0.3 ml [15]. Inhibitor and enzyme were preincu bated for 10 min at 25 °C before the reaction was started by the addition of the arachidonic acid.…”

Interactions of inhibitors of the lipoxygenase and cyclo‐oxygenase pathways with a supplementary binding site on soybean lipoxygenase

“…In contrast to Kuehl et al (1981) and Humes et al (1981) Acetonylacetone bisphenylhydrazone and acetone phenylhydrazone were synthesised in our laboratory from reagent grade materials according to standard procedures as recently described (Baumann & Wurm, 1982 1% (v/v) in the assay system. Appropriate blanks (heat-denaturated enzyme) and controls (ethanolic buffer instead of test drugs) were run through the same procedures.…”

“…The final aim of our studies was to elucidate whether selective cyclo-oxygenase inhibitors or selective lipoxygenase inhibitors or dual inhibitors of both pathways are capable of influencing the inhibitory actions of potent lipoxygenase inhibitors via interactions at a putative supplementary binding site on soybean lipoxygenase. We, therefore, first selected the two highly potent and rather selective lipoxygenase inhibitors, acetonylacetone bisphenylhydrazone (ACACB) and acetone phenylhydrazone (ACPH), which in previous experiments were shown to suppress soybean lipoxygenase activity 15 and 25 times more effectively than rat renal medulla cyclooxygenase (Baumann & Wurm, 1982). We also studied the effects of test compounds on the inhibition of lipoxygenase by phenidone as it has been used previously as a reliable inhibitor of both oxygenation pathways (Blackwell & Flower, 1978;Bailey & Chakrin, 1981).…”