Osamu Hirayama

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The singlet oxygen quenching ability of various naturally occurring carotenoids was examined by measuring toluidine blue-sensitized photooxidation of linoleic acid. To assess quenching, the oxidation of linoleic acid was followed by measuring oxygen consumption and ultraviolet absorbance at 235 nm. We found that oxygen quenching increased as the number of(More)
1. A pure lipid acyl-hydrolase was prepared from potato tubers by acetone precipitation, Sephadex G-100 and DEAE-Sephadex A-50 column chromatography, and by electrofocusing. 2. The purified enzyme was an acidic protein of pI 5.0 and molecular weight of about 70 000. Km values were 0.38 mM for monogalactosyldiacylglycerol and 1.7 mM for phosphatidylcholine.(More)
A sensitive and simple chemiluminescent method for measuring antioxidant activity was developed. The method is based on antioxidant-dependent quenching of chemiluminescence generated from lipid hydroperoxide and isoluminol/microperoxidase reagent. This method was used to evaluate the antioxidant ability of various antioxidants by measuring the(More)
1. Spinach class II chloroplasts were treated with purified potato lipolytic acyl-hydrolase and venom phospholipase A2, and their lipid degradations and the effects on the photochemical activities were followed. 2. Potato lipolytic enzyme hydrolyzed monogalactosyldiacylglycerol at a faster rate than phospholipids such as phosphatidylglycerol and(More)
Spinach class II chloroplasts were treated with snake venom phospholipase A2 in the presence of bovine serum albumin, and separated by sucrose-density centrifugation. The treatment yielded phospholipid-depleted chloroplasts which had lost 82.6% of the original phospholipids. About 20% of the phospholipids of chloroplasts were resistant to enzyme attack.(More)
A lipolytic acyl-hydrolase was purified 520-fold from an homogenate of potato leaves (Solanum tuberosum L. cv. Benimaru). The purified enzyme showed a single protein band on polyacrylamide gel electrophoresis. The enzyme had an isoelectric point of 4.6 and a molecular weight of about 110,000. It had pH optima of 5.5 and 5.0, and Km values of 0.26 and 0.54(More)
Rice bran lipase, phospholipase and galactolipase were extracted, purified and thenn characterized as the enzyme mixtures. All the enzymes were eluted on Sephadex G-100, column as one peak, showing that they have a similar molecular weight around 40,000. On DEAE-Sephadex A-50 column, these enzymes were further separated into two to four components,(More)