Peptidylglycine alpha amidating
Plasma copper has been and continues to be used as a marker of copper status (Milne, 1994).
The vast majority of plasma copper is represented by the cuproenzyme ceruloplasmin (Cp) also known as ferroxidase.
Rodent Cp activity rose during lactation whereas PAM activity fell.
Reduction in Cp activity was more severe than reduction in PAM activity in Cu− offspring and dams.
Furthermore Cp is induced by estrogen, thus activity of Cp is influenced by pregnancy and lactation.
Another potential copper status marker is erythrocyte Cu, Zn-superoxide dismutase (ESOD) activity (Uauy et al., 1985).
Although adults consume approximately the recommended intake of copper daily, pregnant and lactating women, depending on which survey is evaluated, tend not to consume the extra 100–400 µg of copper to meet recommendations (Trumbo et al., 2001).
One of the challenges is to evaluate copper status in this subset of the population and in infants.
Previous research has indicated that the in vitro biochemical activity of PAM is lower in tissues and plasma of copper deficient rats (Prohaska et al., 1995; Peterson and Prohaska, 1999).
ESOD activity may not be as sensitive as Cp because ESOD synthesis would depend on copper release from the liver and delivery to bone marrow.
Furthermore, ESOD levels would reflect a more chronic intake of copper since red cell turnover is much slower than plasma proteins. PAM was discovered to be a cuproenzyme more than 20 years ago in seminal studies (Eipper et al., 1983). One domain binds copper and catalyzes the hydroxylation of the C-terminal glycine in a large number of inactive neuropeptides and is referred to as peptidylglycine-α-hydroxylating monooxygenase (PHM).
With proper controls, each enzyme can be used to assess copper status.
Mammals rely on many exogenous dietary factors to ensure proper development and homeostasis.