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THE HAEMOCYANINS
Author(s) -
REDFIELD ALFRED C.
Publication year - 1934
Publication title -
biological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.993
H-Index - 165
eISSN - 1469-185X
pISSN - 1464-7931
DOI - 10.1111/j.1469-185x.1934.tb01002.x
Subject(s) - hemocyanin , oxygen , chemistry , copper , biochemistry , biology , organic chemistry , genetics , antigen
As yet we know comparatively little about haemocyanin. especially with regard to its relation to oxygen. It is a matter which would well repay investigation to determine whether it has the remarkable properties which haemoglobin has in this respect. properties which are at present unique. (Bayliss, Principles of General Physiology , 1915.) Summary. The haemocyanins are proteins combined with a prosthetic group consisting of a complex copper salt of a sulphur compound and a polypeptide. The physical and chemical properties of haemocyanin are largely due to its protein nature, and the specific differences between the haemocyanins of different groups of animals result largely from the differences in the protein part of the molecule. The combination of haemocyanin with oxygen and the characteristic change in the absorption spectrum which results are, on the other hand, properties of the prosthetic group. The haemocyanin combines with oxygen in all cases in proportion to its copper content, one molecule of oxygen being combined by a quantity of haemocyanin containing two atoms of copper. There is some evidence that at least two modifications of the prosthetic group may occur characterising the Crustacea and cephalopods on the one hand, and the gastropods and Limulus on the other. The equilibrium with oxygen may be described by the mass law if it be assumed that under different conditions one, two, or four prosthetic groups must be oxygenated simultaneously in order to form a stable compound and that under certain conditions a mixture of such forms of the protein exist. In general the oxygenation phenomena displayed by haemocyanin differ from those of haemoglobin only in a quantitative sense. The copper of the prosthetic group is in the cuprous condition but may be oxidised, forming methaemocyanin, by strong agents. Methaemocyanin will combine reversibly with oxygen, forming oxymethaemocyanin. Haemocyanin also combines with carbon monoxide, nitrogen dioxide and with cyanide, forming stable compounds. The physiological function of haemocyanin as a respiratory pigment is well established in the case of the cephalopods. Some correlation exists between the activity of various animals, the oxygen capacity of the blood, and the pressures of oxygen under which the haemocyanin becomes oxygenated.