Water extractability of the zinc protoporphyrin IX-myoglobin complex from Parma ham is pH-dependent.

The bright red color of Parma ham is mainly derived from zinc protoporphyrin IX (ZnPP), which exists in both water-soluble and insoluble states. Water-soluble ZnPP mainly binds to hemoglobin, however, the presence of water-insoluble ZnPP remains unexplained. Therefore, we aimed to elucidate how ZnPP exists in a water-insoluble state by focusing on its binding substance. Depending on the skeletal muscle, water-insoluble ZnPP comprised 30-50% of total ZnPP. The ZnPP water extractability was positively correlated with muscle pH. Water-insoluble ZnPP was extractable with a high-pH solution and existed as a complex with myoglobin or hemoglobin; nevertheless, myoglobin-binding ZnPP was more abundant. Furthermore, the water solubility of the myoglobin globin moiety at pH 5.5-6.0 was reduced by ZnPP binding. These results suggest that water-insoluble ZnPP mainly exists as a ZnPP-Mb complex, with low solubility attributed to the low pH of the ham.

Mapping of the genes for dioecism and monoecism in Spinacia oleracea L.: evidence that both genes are closely linked.

Spinach is basically a dioecious species, with occasional monoecious plants in some populations. Sexual dimorphism in dioecious spinach plants is controlled by an allelic pair termed X and Y located on the short arm of the longest chromosome (x = 6). Ten AFLP markers, closely linked to the X/Y locus, were identified using bulked segregant analysis, four of which were revealed to co-segregate with Y in the present mapping population. We mapped the AFLP markers and two known male-specific DNAs to a 13.4 cM region encompassing the locus. These markers will be the basis for positional cloning of the sex-determination gene. We also showed that a single, incompletely dominant gene is responsible for the highly staminate monoecious character. The gene was found to be located at a distance of 4.3 cM from microsatellite marker SO4, which mapped 1.6 cM from the X/Y locus. This indicates that the monoecious gene seems not to be allelic to but closely linked to the X/Y gene pair. SO4 will enable breeders to efficiently select highly male monoecious plants for preferential use as the pollen parent for hybrid seed production.