Hemocyanin copper content

The stability of the black copper complex and its tendency to form soluble, highly colored complexes with amines (and also denatured albumen) indicates that the compound we have in hand is involved in the union of the copper to the protein in hemocyanin. The function of the prosthetic group thus appears to be the same as that of protoporphyrin in hemoglobin, namely, to provide a basis for a very stable metallic complex. Beyond this analogy, however, there seems to be little or no chemical relationship between the prosthetic groups in limulus hemocyanin and hemoglobin. It should be noted that since limulus hemocyanin differs markedly in its copper content from the hemocyanin of other species,2 the conclusions we have drawn do not necessarily apply to the nature of the prosthetic group in the other hemocyanins. 

Data on the elementary composition of hemocyanins from many species are reported in Table V. According to their copper content hemocyanins are divided in two groups those of molluscs in which it amounts to 0.24-0.26% of the dry weight and those of arthropods in which it accounts for only 0.17-0.18%. Discrepancies in the values reported by earlier authors must be attributed either to impurities present or to the method of determination. The hemocyanins do not contain any heavy metal other than copper (Gatterer and Philippi, 1933). Hernler and Philippi (1933) measured 11.5% water in crystalline hemocyanin, a relatively low value compared with other proteins. The sulfur content is also fairly low, 0.7-1.2% in all hemocyanins examined, and appears to have no relation with the copper content. In hemocyanin from Umultts poliphemus the sulfur derives half from cystine and half from methionine (Mazur, 1937). 

According to Ranzi (1938) hemocyanin is formed in the embryo of Sepia at the XVIth Naef s stage of development and the copper content, which equals 9 X 10 mg. in the egg at the beginning of development, is ten times as great in hatching embryo. The adult animal contains notable quantities of copper but it is not known how much of it derives from sea water and how much from food. Only with Phascolosoma hemerythrin have experiments been performed on the incorporation of radioactive iron (Schulman, 1957). The incorporation is fifteen times greater in hemolyzed cells than in whole cells because of the low permeability of the cell membranes towards ferric ions. According to the... 

Whereas in crustaceans 90% of the copper is, under normal conditions, in the form of hemocyanin (Zuckerkandl, 1957), the copper in the hemo-cyanin of molluscs Octopus) represents scarcely 8 to 10% of the total copper present, more than 75% being found in the hepatopancreas, partly as free copper and partly bound organically the copper found in all the other organs represents only very small amounts of the total (Ghiretti and Spencer Bernard, unpublished). Furthermore, in crustaceans, according to Zuckerkandl (1957) who studied the relationships between the copper of the hemolymph and that of the hepatopancreas, the hemocyanin content of the blood is lowered during molting almost to zero. At this time 50% of the copper is accumulated in the hepatopancreas and the rest is excreted. 

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