Chlorocruorin 



H. MUNRO FOX 



Chlorocruorin is a red-green dichroic respiratory protein only 

 found dissolved in the blood plasma of certain marine worms. It is 

 chemically closely related to haemoglobin. Spectroscopically its 

 haem is nearer to that of cytochrome a than to protohaem. 

 Chemically it differs from protohaem by the oxidation of one vinyl 

 group. Chlorocruorin has a low affinity for oxygen and a higher 

 affinity for carbon monoxide than any haemoglobin. Serpula has 

 both chlorocruorin and haemoglobin in its blood. Chlorocruorin 

 has never been found within a cell ; those animals which possess it 

 in their blood have protohaem, not chlorocruorohaem, in their tissues. 



There exist four coloured proteins with a respiratory function which 

 are found in the blood or body-cavity fluid of animals. These are 

 haemoglobin, chlorocruorin, haemocyanin and haemerythrin. The 

 first two are close chemical relatives. Chlorocruorin is dichroic, being 

 red when concentrated, green when dilute. The only place in which 

 it is found is in solution in the blood of certain marine polychaete 

 worms, particularly of the group Serpulimorpha. This pigment received 

 its very appropriate name from Ray Lankester in 1867. His pioneer 

 studies established its similarity to haemoglobin, but from that time 

 until 1925 chlorocruorin was almost completely neglected. In the 

 latter year Sir Joseph Barcroft pointed out to me that there must be 

 pigments among the invertebrate animals which are somewhat like 

 haemoglobin but different from it. Stimulated by this, I went to the 

 marine biological station at Roscoff in Brittany and started to inves- 

 tigate chlorocruorin in the blood of Spirographis (Sabella spallanzanii) 1 . 

 Chlorocruorin, oxygenated and deoxygenated, has absorption 

 spectra analogous to those of haemoglobin, but the bands are shifted 

 towards the red end of the spectrum. Its derivatives, such as the 

 haemochromogen and the porphyrin, likewise have bands whose axes 

 have longer wave lengths. Spectroscopically, chlorocruorohaem 

 (which Warburg subsequently misnamed ' Spirographishamin ') recalls 

 the haem of cytochrome a, in that each of them forms haemochro- 

 mogens with a-bands towards the red end of the spectrum. The 

 pyridine-haemochromogen of chlorocruorohaem has its a-band at 

 583 mtx, that of cytochrome a at 587 mpt, while that of the protohaem 

 of haemoglobin is at 557 mu.. Chlorocruoroporphyrin has been found 



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