Peptidylglycine alpha amidating
We report our findings of plasma copper, ceruloplasmin, PAM, and the Cu SI of PAM measured in these patients and discuss the possible usefulness of these determinations for the diagnosis of mild copper deficiency in humans. Three male patients (5-39 y) from one family were identified as having a Menkes disease variant with occipital horns which results from a mutation in the Menkes disease gene(MNK).
MNK encodes a protein similar to copper-transporting P-type ATPases.
We hypothesized that these determinations are also suitable for the assessment of copper nutriture in humans, and tested this hypothesis by determining PAM activity and the Cu SI of PAM in plasma samples obtained from one family of three male patients with occipital horns and Menkes disease variant, and comparing these to the values obtained from healthy male control subjects.
A Menkes disease phenotype with occipital horns is characterized by a less severe degree of neurodegeneration, growth retardation, and abnormalities of connective tissues compared with the classic Menkes disease.
The interassay coefficient of variation of these analyses is approximately 4%.
Plasma copper will parallel plasma ceruloplasmin changes.
The combination of these two determinations may provide a means for the assessment of copper nutriture in humans using blood samples obtained in a single microhematocrit tube.
Further investigation is warranted to evaluate whether these noninvasive measurements can be used for the diagnosis of mild copper deficiency in humans with sufficient specificity and sensitivity.
The Cu SI values of plasma PAM activity were significantly higher in patients than in the control subjects.
The higher Cu SI among patients with Menkes disease variant may indicate higher levels of PAM apoenzyme in severe copper deficiency than under copper-sufficient conditions.