Development and application of novel enzyme inhibitors for the preservation of freshness of marine products using a library of marine microorganisms

已知冷适应酶是导致海产品变质的原因。为了保持海产品的新鲜度，本研究旨在从天然来源中鉴定酶并寻找其抑制剂。为了获得冷适应酶，我们从日本各地的海洋动物肠道内容物中校正了3，000多株海洋细菌。我们已经筛选出有价值的菌株，指示脂肪酶活性和磷脂降解酶活性（磷脂酶A1，磷脂酶C，溶血磷脂酶C和鞘磷脂酶活性）。最后，我们确认了培养液中约100株具有脂肪酶活性的菌株，约10株具有磷脂降解酶活性的菌株。我们计划同时从之前分离到的所有海洋微生物中对这些酶进行表征，并寻找这些海洋脂质降解酶的特异性抑制剂，本研究还尝试从不同地区的海水和海洋沉积物样品中分离产生酪氨酸酶抑制剂的海洋微生物。一个菌株，产生酪氨酸酶抑制剂，分离从新岛外海100米深的岛屿，并选择进一步的研究，它的鉴定和生产的抑制剂。经鉴定该菌株为木霉属（Trichoderma sp.）。发现活性物质为低分子量肽。粗品抑制剂可防止虾等甲壳类动物的褐变反应，表明该抑制剂可能适用于渔业。

Cold-adapted enzymes are known to be cause for debasement of marine products. To preserve freshness of marine products, our present study was designed to characterize the enzymes and to search their inhibitors from natural sources.In order to obtain the cold-adapted enzymes, we have corrected over 3,000 strains of marine bacteria from the intestinal contents of marine animals in various regions in Japan. We have screened valuable strains indicating lipase activity and phospholipid-degrading enzyme activities (phospholipase A1, phaspholipase C, lyzophospholipase C and sphingomyelinase activities). Finally, we have confirmed around 100 strains with lipase activity, and around 10 strains with phospholipids-degrading enzyme activities in the culture solution. We are planning to characterize these enzymes and to search their specific inhibitors for these marine lipid-degrading enzymes from all marine microorganisms isolated before at once.In the present study, an attempt was also made to isolate tyrosinase inhibitor-producing marine microorganisms from seawater and marine sediment samples of various areas. One strain which produced a tyrosinase inhibitor was isolated from Off-Niijima Islands at a depth of 100 m and was selected for further studies on the identification of it and production of the inhibitor. Base on the taxonomical characteristics, the strain was identified as Trichoderma sp. The strain produced the inhibitor when cultivated in seawater medium with shaking. The active substance was found to be a low molecular weight peptide. The crude inhibitor prevented the darkening reaction of crustaceans such as shrimp they are stored, suggesting that this inhibitor might be applicable to fisheries.