open access

https://doi.org/10.14943/doctoral.k15296

https://hdl.handle.net/2115/94647

亜硝酸塩/硝酸塩無添加食肉製品中におけるヘムの解離を介したヘムタンパク質からの亜鉛プロトポルフィリンIX の形成機構に関する研究

英語

2023-03-23

Hokkaido University

86p

This study was carried out to investigate the formation mechanism of the water-soluble ZnPP, which was the main ZnPP existence state in Parma ham, in the nitrite/nitrate-free dry-cured meat products using a newly established experimental model. First, a new experimental model to produce higher amount of water-soluble ZnPP complexes was optimized. Mainly the water-soluble ZnPP complex formed in this model was ZnPP-Hb dimer and was the same as that in Parma ham, indicating this new experimental model was suitable for studying the formation of water-soluble ZnPP. The addition of the exogenous Hb in the new model promoted higher ZnPP formation and released non-heme iron content than with Mb added, and the heme-globin binding stability of Hb was lower than that of Mb under the anaerobic conditions. These results indicated that compared with Mb, Hb may be easy to release heme as the substrate to form ZnPP due to its unstable heme-globin binding and may simultaneously produce apo-Hb. After only mixing the apo-Hb solution with the ZnPP standard, the ZnPP-Hb complex was formed, indicating ZnPP-Hb could form by non-enzymatically inserting ZnPP into the apo-Hb. As for ZnPPMb, its formation pathway is speculated to be similar to that of ZnPP-Hb, but the stable heme-globin binding of Mb may result in its less heme dissociation, leading to less ZnPPMb formation. On the other hand, the exogenous Hb could bind with the NO, which was derived from nitrite, to form NOHb. The NOHb showed a more stable heme-globin structure and lower heme dissociation amount during anaerobic incubation compared with the exogenous OxyHb. Also, the exogenous addition of NOHb to the experimental model had no supplemental effect on ZnPP formation. These results indicated that the NOHb was hard to dissociate heme to convert to ZnPP due to its stable heme-globin binding. Moreover, after the hematin released from the Hb and mHb, it needs previously reduce to heme and then converted to ZnPP. In contrast, the excessive reductant addition to the meat homogenate significantly suppressed the formation of ZnPP, which may because the over reduction suppressed the heme protein autoxidation, further limited their hematin dissociation. In conclusion, Hb was the dominating substrate to form ZnPP because heme/hematin was easy to dissociate from Hb and autoxidized mHb due to their unstable heme-globin binding, and produced apo-Hb simultaneously. After the dissociated hematin was reduced to heme, the heme mainly dissociated from Hb was converted to ZnPP, followed by non-enzymatically inserting into apo-Hb to form the ZnPP-Hb complex in the nitrite/nitrate-free dry-cured meat products.

2023-03-23

甲第15296号

博士(農学)

(主査) 准教授 若松 純一, 教授 玖村 朗人, 教授 西邑 隆徳, 助教 早川 徹, 教授 後藤 貴文 （環境科学院）

農学院（農学専攻）

博士論文

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