Chlorocruorin

1992, N. B. Terwilliger, Chapter 8: Molecular Structure of the Extracellular Heme Proteins, Ch. P. Mangum (editor), Advances in Comparative & Environmental Physiology 13: Blood and Tissue Oxygen Carriers, Springer-Verlag, 1992 softcover reprint, page 203, It was earlier thought that chlorocruorin was very different from hemoglobin based on a subunit structure with a mass of 34-35 kDa (Antonini et al. 1962; Guerratore and Zito 1977). […] Some writers have questioned the value of drawing a distinction between the chlorocruorins and hemoglobins, especially from an evolutionary point of view (Mangum 1985; see also Toulson, Chap. 9, this Vol.). The visual phenomenon of green blood has perhaps led to a stronger distinction between chlorocruorin and hemoglobin than warranted.

Later it was shown that the α-bands of the pyridine haemochromogens of both cytochrome a and chlorocruorin resemble each other closely (Keilin, 1933 a).

The affinity of chlorocruorin for oxygen is equivalent to the haemoglobin. It is interesting that within the same family of worms like [S]abellidae, [S]erpulidae and [A]mphotritidae same^([sic]) species have chlorocruorin while others have haemoglobin.