Phospholipids are major components of cellular membranes that participate in a range of cellular processes. Phosphatidic acid (PA) is a key molecule in the phospholipid biosynthetic pathway. In Saccharomyces cerevisiae, SLC1 has been identified as the gene encoding lysophosphatidic acid acyltransferase, which catalyzes PA synthesis. However, despite the importance of PA, disruption of SLC1 does not affect cell viability (Nagiec, M. M., Wells, G. B., Lester, R. L., and Dickson, R. C. (1993) J. Biol. Chem. 268, 22156 -22163). We originally aimed to identify the acetyl-CoA:lyso platelet-activating factor acetyltransferase (lysoPAF AT) gene in yeast. Screening of a complete set of yeast deletion clones (4741 homozygous diploid clones) revealed a single mutant strain, YOR175c, with a defect in lysoPAF AT activity. YOR175c has been predicted to be a member of the membrane-bound O-acyltransferase superfamily, and we designated the gene LPT1. An Lpt1-green fluorescent protein fusion protein localized at the endoplasmic reticulum. Other than lysoPAF AT activity, Lpt1 catalyzed acyltransferase activity with a wide variety of lysophospholipids as acceptors, including lysophosphatidic acid, lysophosphatidylcholine, lysophosphatidylethanolamine, lysophosphatidylglycerol, lysophosphatidylinositol, and lysophosphatidylserine. A liquid chromatography-mass spectrometry analysis indicated that lysophosphatidylcholine and lysophosphatidylethanolamine accumulated in the ⌬lpt1 mutant strain. Although the ⌬lpt1 mutant strain did not show other detectable defects, the ⌬lpt1 ⌬slc1 double mutant strain had a synthetic lethal phenotype. These results indicate that, in concert with Slc1, Lpt1 plays a central role in PA biosynthesis, which is essential for cell viability.

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The antioxidant activities of several extracts from Susabinori (Porphyra yezoensis) were measured by the ferric thiocyanate method and the thiobarbituric acid method. The methanol, acetone, ethyl acetate, and hexane extracts, and the chloroform-soluble and water-soluble fractions from the chloroform-methanol extract exhibited higher activities than α-tocopherol. The hot water extract showed little activity. Thinlayer chromatography analysis of the active extracts suggested the existence of several antioxidants. The activity of the chloroform soluble fraction was due to chlorophyll analogs. A strong antioxidant was isolated from the methanol extract, accompanied by several amino acids such as leucine and phenylalanine. This compound was identified as usujilene, a kind of mycosporine-glycine like amino acid.Paper no. J8916 in JAOCS 76, 649-653 (May 1999).Seaweeds, such as laver and kelp, are commonly eaten in Japan and their high dietary fiber and vitamin content have stimulated their evaluation as health foods. In addition, seaweeds contain high levels of polyunsaturated fatty acids (1). Although polyunsaturated fatty acids are very easily oxidized, seaweeds are known to resist oxidation during storage. Fujimoto et al.(2) reported the antioxidant effect of 21 species of marine algae and found that the phospholipid fraction in arame (Eisenia bucyclis) showed efficient activities. Tutour (3) described that brown algae had strong antioxidant activity and that they synergistically enhanced the effect of vitamin E. Furthermore, Nishibori et al. (4) identified pheophytin a, one of the chlorophyll analogs, as a major antioxidant in Aonori (Enteromorpha sp.). In this paper, we describe the antioxidant effect of several extracts from Susabinori (Porphyra yezoensis), one of laver, and the isolation of antioxidants from the methanol extract. EXPERIMENTAL PROCEDURESMaterials and extraction. Cultured P. yezoensis was purchased from Akashiura Fisherman's Union (Hyogo, Japan) in February 1995. A part (10 g each) of the ground freeze-dried material was extracted independently with 200 mL of n-hexane, ethyl acetate, acetone, chloroform/methanol (2:1), methanol, and hot water (90°C) under stirring. Each extract was filtered and concentrated in vacuo. Water was added to the chloroform/methanol extract and then partitioned with chloroform to afford a chloroform-soluble fraction and an aqueous fraction. Antioxidative assay. (i) Ferric thiocyanate method (FTC). The method of Kikuzaki et al. (5) was slightly modified. To a mixture of 2 mg of the fractions of the Susabinori extract, α-tocopherol or isolated compounds in 2 mL of 99.5% ethanol in a vial (φ = 35, h = 80 mm), 2.05 mL of 2.51% linoleic acid in 99.5% ethanol, 4 ml of a 0.05 M phosphate buffer (pH 7.0), and 1.95 mL of water were added. The solution including linoleic acid without any antioxidant or extract was used as control. The vial was placed in an oven at 40°C in the dark. At each test time, to 0.1 mL of this sample solution were added 9.7 mL of 75% ethanol and 0.1 mL of 3...

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