Preliminary Identification of Lipoxygenase in Algae (Enteromorpha intestinalis) for Aroma Formation

Abstract

Lipoxygenase (LOX) activity was identified in a green sea algae (Enteromorpha intestinalis). The oxygen consumption rate of sea algae-catalyzed oxidation of linoleic acid was 1.18 μmol/min·mg of protein. The catalytic rate was 911 times that of shrimp hemolymph LOX and 59 times that of trout gill LOX. Based on retention time in normal phase HPLC analysis and UV absorption spectrosocopy, hydroperoxidation of linoleic acid by sea algae LOX was at the C9 and C13 positions with a ratio of 1.97:1. The products of sea algae LOX treated with arachidonic acid were 12- (or 8-) and 15-HETE (hydroxyeicosatetraenoic acid) on the basis of retention time in reverse phase HPLC analysis. Thus, 12- (or 8-) and 15-LOX were the major LOX isozymes in the sea algae. The optimal pH of sea algae LOX was 7.8 and the optimal temperature was around 35 °C. Different treatments of sea algae generated volatile compounds contributing to flavor notes of clam, oyster, fresh apple, cucumber, mango, and algae identified with the GC-sniffing method. This is the first observation of LOX in marine algae with respect to its possible roles in seafood flavor formation. Keywords: Lipoxygenase; sea algae; seaweed; Enteromorpha intestinalis; flavor