Respiratory pigments and

The seven consecutive amino-acid residues shown in the table comprise residues numbers 56 to 62 in the a-chain and numbers 61 to 67 in the i8-chain, counting from the amino end. Three of the seven residues are shown to be substituted in some normal respiratory pigments and the changes, as in the ovine a-chain and in one of the orangutan chains, may involve the substitution of an acid for a neutral amino acid without any fundamental interference with hemoglobin function. Of course such substitutions would be expected to affect one or several of the physical parameters of oxygenation. 

Keilin, D. (1925). On cytochrome, a respiratory pigment common to animals, yeasts and higher Plants. Proc. Roy. Soc. B 98, 312-329. 

I must admit that this first visual perception of an intracellular respiratory process was one of the most impressive spectacles I have witnessed in the course of my work. Now I have no doubt that cytochrome is not only widely distributed in nature and completely independent of haemoglobin, but that it is an intracellular respiratory pigment which is much more important than haemoglobin. 

Biochemical evolution refers to changes over geologic time of the fundamental composition of organic components—e.g., the sequence of amino acids in protein molecules. The best documented example of biochemical evolution is that of the respiratory pigment haemoglobin, and the relation of its evolution to the fossil record has been summarized recently (58). Many of the monographs on comparative biochemistry have discussed biochemical evolution (59, 60, 61), and the reader is... 

Chlorins are the respiratory pigments in plants, and haemoglobin the respiratory pigment in the higher animals 62,64)-... 

Respiratory pigments similar to the vertebrate haemoglobins have also been identified in many invertebrates. These vary from small proteins with two Fe-porphyrin units to large molecules containing up to 190 Fe-porphyrin units. Myoglobin, the 02 storage protein in muscle tissue, is also a small iron-protoporphyrin protein. The crystal structures of this and a number of other porphyrin proteins are now known (Chapter 20.2, Table 11). 

Keilin D (1925) On cytochrome, a respiratory pigment, common to animals, yeast, and higher plants. Proc R Soc Lond B 98 312-339... 

In 1886, MacMunn 12) discovered the respiratory pigment, myohema-tin, which was widely distributed in plant and animal tissues. This important observation attracted little attention at the time of its publication and became effectively lost in the literature 13). In 1925, Keilin 14)... 

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