Zinc protoporphyrin IX (ZnPP) is the dominant red pigment in nitrate/nitrite free dry-cured hams such as Parma ham. A large amount of ZnPP in Parma ham is water-extractable and is thought to exist in complexes with unidentified water-soluble proteins. This study was done to clarify these ZnPP-binding proteins to provide insight into the ZnPP-forming mechanism. The ZnPP-binding proteins were purified from Parma ham water extract (PHE) through a combination of hydrophobic interaction chromatography, urea-PAGE, and SDS-PAGE, and finally identified as hemoglobin (Hb) and myoglobin (Mb). According to western blotting analysis of PHE, ZnPP-Hb and ZnPP-Mb complexes were observed as both intact and proteolyzed forms, and the formation of these complexes was independent of proteolysis. The amount of total ZnPP-Hb complexes was ~3-fold higher than total ZnPP-Mb complexes. These results suggested that the heme destabilization in the heme pocket is important rather than proteolysis for forming ZnPP-binding proteins.

锌原卟啉IX（ZnPP）是无硝酸盐/亚硝酸盐的干腌火腿（如帕尔马火腿）中主要的红色颜料。帕尔马火腿中大量的ZnPP可以通过水萃取，并被认为与未知的水溶性蛋白质形成复合物。进行这项研究是为了阐明这些ZnPP结合蛋白，以提供有关ZnPP形成机理的见解。ZnPP结合蛋白通过疏水相互作用色谱，尿素-PAGE和SDS-PAGE的结合从帕尔马火腿水提取物（PHE）中纯化，最终鉴定为血红蛋白（Hb）和肌红蛋白（Mb）。根据对PHE的蛋白质印迹分析，观察到ZnPP-Hb和ZnPP-Mb复合物既完整又被蛋白水解，而且这些复合物的形成与蛋白水解无关。ZnPP-Hb复合物的总量比ZnPP-Mb复合物高约3倍。这些结果表明，血红素口袋中的血红素去稳定作用对于形成ZnPP结合蛋白而言很重要，而不是蛋白水解作用。