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Lipoxygenase was purified homogeneously from cups of Pleurotus ostreatus by Sephacryl S-400 HR gel filtration, Dyematrex Green A affinity, and DEAE-Toyopearl 650M ion-exchange chromatographies. The molecular weight of the enzyme was estimated to be 67,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 66,000 by gel filtration; the isoelectric point was pH 5.1. The optimum pH and temperature of the enzymatic activity were 8.0 and 25 degrees C, respectively. The enzyme contained non-heme iron, and a thiol group seemed to be involved in its activity. The K(m), V(max), and k(cat) values of the enzyme for linoleic acid were 0.13 mM, 23.4 micromol.min(-1).mg(-1), and 25.7 s(-1), respectively. The enzyme showed high specificity toward linoleic acid. When linoleic acid was incubated with the enzyme, 13-hydroperoxy-9Z,11E-octadecadienoic acid was found to be the main oxidative product.

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Alzheimer's disease and type 2 diabetes are very serious diseases with the latter having been suggested to cause the former. We prepared super-hard rice bread blended with black rice bran (SRBBB), which contained a high amount of resistant starch that showed strong inhibitory activities against β-secretase and acetylcholinesterase even after heating. Black rice bran showed greater β-secretase inhibitory activity (3.6-fold) than Koshihikari rice. The bran contained more oleic acid and anthocyanin, meaning that it is potentially a biofunctional food with a high antioxidant capacity. Furthermore, aged mice, which were fed a SRBBB diet for four weeks, showed lower amyloid β 40 peptide in the blood than mice fed a commercial diet (p < 0.01). Additionally, their initial blood glucose levels (BGLs) after 12 weeks of being fed SRBBB were significantly lower than those in the control group. Taken together, our results indicate SRBBB shows promise for inhibiting not only amyloid β production, but also abrupt increases in postprandial BGLs.