Dioxygenation of N-linoleoyl amides by soybean lipoxygenase-1

Abstract

Anandamide, a novel neurotransmitter, has been reported to be dioxygenated by brain lipoxygenase (Hampson et al. (1995) Biochim. Biophys. Acta 1259, 173-179 and Ueda et al. (1995) Biochim. Biophys. Acta 1254, 127-134). Anandamides constitute a new class of neuroregulatory fatty acid amides. However, little is known about the enzymatic dioxygenation of these lipids. Therefore, we have tested several members of the neuroactive fatty acid amide class containing a 1Z,4Z-pentadiene system whether they could be dioxygenated by soybean lipoxygenase-1, which is a model enzyme for mammalian lipoxygenases. In this study it was found that lipoxygenase-1 converts N-linoleoylethanolamide (ODNHEtOH), N-linoleoylamide (ODNH2), N-linoleoylmethylamide (ODNHMe) and N,N-linoleoyldimethylamide (ODN(Me)2 into 13-(S)-hydroperoxy-9Z,11E-octadeca-9,11-dienoyl amides derivatives. The apparent Km values for ODNHEtOH (23.6±3.7 mu M), ODNH2 (8.60±0.65 mu M) and linoleic acid (OD: 8.85±0.74 mu M) are not significantly different. The kcat for ODNH2 (32.4±1.2 s−1) is twice as small as compared to the turnover numbers of the other substrates, viz. ODNHEtOH (61.6±5.0 s−1) and OD (54.4±2.0 s−1). The results suggest that N-linoleoyl ethanolamide and N-linoleoyl amide can be readily converted by lipoxygenases in vivo.