Copper proteins and ferroxidases in human plasma and that of wild-type and ceruloplasmin knockout mice

Abstract

In the blood plasma of humans and rats, ceruloplasmin is the major copper-binding protein and ferroxidase, accounting for 70% of the copper present in the plasma, with the rest binding primarily to albumin and a macroglobulin. Systematic studies with fresh plasma were carried out to compare what occurs in the mouse. C57BL6 mice had half as much copper and pPD (p-phenylene diamine) oxidase activity as humans and rats, 20-40% as much ferroxidase activity as humans (determined using three different assays) and less inhibition by azide. Plasma from ceruloplasmin knockout mice had no pPD oxidase activity, but retained >50% ferroxidase activity (which was not as affected by azide). Modelling of mouse ceruloplasmin against the known X-ray structure of human ceruloplasmin indicated subtle but potentially significant changes in the pPD- and azide-binding sites. Purification and in-gel assays after native PAGE confirmed that mouse ceruloplasmin had ferroxidase activity but revealed an additional ferroxidase in ceruloplasmin knockout mouse plasma, which is also seen in size-exclusion chromatography. In the wild-type mouse, the 'ceruloplasmin' peak contained approximately 55% of the total copper, but ceruloplasmin knockout plasma exposed a major additional peak (180 kDa) which co-eluted with ferroxidase activity. Two other ferroxidases (700 and 2000 Da) were also detected in mouse and human plasma. Mammalian blood thus contains copper components and ferroxidases not reported previously.

A Comparison of the Behavior of 64Cu-Acetate and 64Cu-ATSM In Vitro and In Vivo

“…It should finally be noted that copper metabolism in mice has both similarities to and differences from humans, with decreased plasma copper levels in mice, compared with humans. Differences also exist in secondary copper binding proteins but with the liver as a significant copper reservoir in both species (38,39). These data further suggest that the relationship between Cu-ATSM uptake and hypoxia is not entirely direct in vivo, in contrast to results from experiments in tissue culture.…”

Relationship of blood and seminal plasma ceruloplasmin, copper, iron and cadmium concentrations with sperm quality in Merino rams

“…Volume ( min and transcuprein (approximately 15% and 10% of the total Cu, respectively) (Gray et al, 2009). Seminal plasma Cu concentrations were reported to be 0.5 ppm in ram (Cole and Cupps, 1969) which were higher from the results in the current study.…”

Altered transition metal homeostasis in Niemann–Pick disease, type C1

“…In parallel with the elevated plasma copper levels at P49 in Npc1 −/− mice, we also observed a 49 ± 4% increase (p = 0.0004) in total CP compared to WT (Figure 2D). This was also reflected in a concomitant 53 ± 7% increase (p < 0.0001)in total oxidase activity, the sum of azide-sensitive activity (attributed to CP, and known as ferroxidase I) and azide-resistant activity (ferroxidase II, which is proportionally more in mice than in humans) 36 (Figure 2E). Although there was no age-dependent change in total CP levels in Npc1 −/− mice, there was an age-dependent increase in the copper-bound active holo-CP level and a decrease in the unmetallated apo-CP level (Figure 2F).…”

“…In this study we further demonstrated that this corresponds to increased copper-bound holo-CP and CP oxidase activity (Figure 2F and 2G). This difference between human and mouse plasma CP and its oxidase activity may be explained by a species-specific difference in CP metabolism and activity 36 . In humans, CP accounts for 90 – 100% of the plasma ferroxidase activity.…”