ON THE REACTION SPECIFICITY OF THE LIPOXYGENASE FROM TOMATO FRUITS

A lipoxygenase was purified 300-fold from a homogenate supernatant of ripe tomato fruits by fractionated ammonium sulfate precipitation and anion exchange fast protein liquid chromatography. The specific linole ate oxygenase activity of the final enzyme preparation was 1300 nkat p er mg protein at pH 6.8 and 25 degrees C in the absence of any deterge nt. The enzyme oxygenated linoleic acid and a-linolenic acid at compar able rates, whereas gamma-linolenic acid, arachidonic acid, 11,14-eico sadienoic acid and 11,14,17-eicosatrienoic acid were poor substrates. Linoleic acid was converted to 9(S)-hydroperoxy-10E, 12Z-octadecadieno ic acid, whereas 5(S)-HpETE, 11(S)-HpETE and 8(S)-HpETE were identifie d as major oxygenation products from arachidonic acid. The tomato lipo xygenase did not react with either dilinoleyl phosphatidylcholine or t he lipid extract from beef heart mitochondria. The possible biological importance of the reaction of tomato lipoxygenase with arachidonic ac id is discussed.