This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Ultraviolet (UV)-absorbing compounds from natural sources are attracting interest as potential ingredients for cosmetics and other protective materials. Saclipins A and B are unusual UV-absorbing oxylipins produced by the edible freshwater cyanobacterium Aphanothece sacrum, known in Japan as Suizenji-nori.
Although these compounds show promising UV-absorbing and other functional properties, their low natural abundance and poorly understood biosynthesis have limited efforts to use them more broadly. Saclipin accumulation is strongly stimulated by desiccation stress, and the compounds have also been reported to show antioxidative and antiglycative activities as well as photo- and thermochemical stability. Understanding how saclipins are made could therefore help researchers develop production approaches that do not depend entirely on extracting them from the cyanobacterium.
To address this challenge, professor Hakuto Kageyama and graduate student Yoshie Uchida from the Graduate School of Environmental and Human Sciences, Meijo University, Japan, led a research team. The researchers searched the A. sacrum genome and identified two candidate lipoxygenase enzymes, AsLOX1 and AsLOX2. They produced recombinant versions of both enzymes and tested their ability to act on α-linolenic acid (ALA), linoleic acid and arachidonic acid.
AsLOX2 showed clear activity toward all three substrates, with the highest activity toward ALA, whereas AsLOX1 showed no detectable activity under the tested conditions. Their findings were published online in the Journal of Natural Products. Further experiments revealed that AsLOX2 acts on ALA in a distinctive way, introducing oxygen at two positions to produce 9,16-diHPOTE, a key intermediate linked to saclipin formation.
The researchers confirmed the identity of this intermediate using chromatographic and mass spectrometric analyses. Under optimized conditions, AsLOX2 converted more than 80% of the starting fatty acid into 9,16-diHPOTE within a few minutes, highlighting the enzyme's strong activity. "Identifying AsLOX2 as the gateway enzyme gives us an important biochemical entry point for understanding how this unusual UV-absorbing compound is produced," says Kageyama.
The team then tested whether 9,16-diHPOTE could be converted into saclipins through a series of chemical reactions. First, the intermediate was reduced to form 9,16-diHOTE. The researchers then used a chemical oxidation step to generate compounds corresponding to saclipins A and B, confirming their identities through comparison with authentic compounds.
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