Studies on the contribution and reaction mechanism of cuproproteins for melanization in crustaceans

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K07574
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic life science
• Research Institution: Kyoto University
• Principal Investigator: Masuda Taro 京都大学, 農学研究科, 助教 (40395653)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 甲殻類 / 黒変 / メラニン形成 / 銅タンパク質

Outline of Final Research Achievements

Melanization or black spot formation in crustacean is one of the most serious problems on food industry. Phenoloxidases (PO) and hemocyanins (Hc), both of which are cuproprotein, are the candidates of the enzyme that mainly causes the melanin formation. In this study, I have investigated the real source of the enzymatic activity for melanin formation. Although Hc is an extreamly abundant protein, it did not show detectable PO activity. On the other hand, PO showed prominent PO activity and it contributed to almost all the PO activity in hemolymph of some shrimp species. Further, we have identified some molecular species of PO, each of which showed distinctive feature in terms of the localization and maturation process. It was also suggested that the dominant molecular type of PO was varied among shorimp species.

Free Research Field

水産生物化学

Academic Significance and Societal Importance of the Research Achievements

黒変反応の原因酵素については、当初から知られていたフェノールオキシダーゼ(PO)の他に、近年甲殻類の酸素運搬タンパク質であるヘモシアニン(Hc)が関与する可能性も指摘されていた。本研究では、国産の主要な食用甲殻類数種におけるPO活性を指標に、甲殻類黒変現象の原因タンパク質精製し、この酵素活性はほぼPOに依存していることを明らかにした。Hcは、POと類似の構造を持ち、甲殻類体液中に極端な高濃度で存在するが、酵素活性はほぼ認められず、極めて微弱な活性を持ち得るか否かは今後の検討課題である。