Studies on the post-mortem fish muscle tenderization -Analysis using the transgenic red seabream

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By the injection of 1, 10-phenanthroline, a specific inhibitor for metalloproteinase, meat tenderization of red seabream was significantly suppressed, suggesting that matrix metalloproteinase is involved in the post-mortem meat tenderization of red seabream. Then, Genes encoding matrix metalloproteinases (MMP) and tissue inhibitor of metalloproteinases (TIMP) were isolated from red sea bream. Actually, recombinant MMP degraded collagen, a main component of the muscle connective tissue, and the activity was inhibited by the addition of TIMP. These facts suggested MMP-TIMP system plays a very important role in the post-mortem tenderization of red seabream muscle.These findings suggested the transgenic expression of TIMP might suppress the post-mortem meat tenderization. We made a transgenic medaka overexpressing TIMP. Histological analysis demonstrated the effectiveness of the transgenic expression of TIMP for the suppression of collagen breamdown.To apply this technology to cultured fish, we adopted red seabream, an important species for fish culture. For the construction of the expression vector, three distinct α-actin genes (two skeletal muscle types and one cardiac muscle type) were also isolated. These actin genes are composed of 8 exons and having E Box and CArG Box in the up-stream region, but the expression pattern in the fish was clearly distinct. We made the expression vectors harboring the promoter regions of these genes with GFP as a reporter gene. As a result, all vectors were revealed to be useful for making transgenic red seabream.By using these vectors, we introduced TIMP gene into red seabream. We are now keeping 200 fish possibly having TIMP gene.