Sipunculus Hemerythrin

According to Roche, the iron content of Sipunculus hemerythrin is 1.01%. Kubo (1953a), using the pigment from Phascolosoma, also... 

However, as mentioned above, hemerythrin of Sipunculus nudus contains 10 iron atoms and only 2 cystine residues per molecule of protein (Holleman and Biserte, 1958). If, according to Klotz s theory, only the iron atoms which are linked to the protein through -SH groups operate in the oxygenation reaction, most of the iron of Sipunculus hemerythrin would be inactive, in contrast with the data on the iron-oxygen ratio. 

Hemerythrin. The iron-containing blood pigment of various marine worms Sipunculus, Phascolopsis) as well as the genus Lingula of the brachiopods dating back to the Silurian period (ca. 400 million years ago) and still present in the oceans today. H. is - in contrast to the heme derivatives - a non-heme iron protein (Mr 108000) made up of 8 subunits, each with two Fe(ll) ions directly bound to the protein. Each subunit... 

This method is time-consuming and during the long term dialysis the protein can easily undergo irreversible changes. Moreover, only a small part of it is transformed into crystals. Preparations of pure hemerythrin from Sipunculus nudur, useful for analytical work, can be obtained by paper electrophoresis in Veronal buffer pH 8.9 (Holleman and Biserte, 1958). 

According to Florkin (1933) crystals of hemerythrin from Phascolosoma elongatum appear as thin octahedral tabular plates. More accurate examination reveals that the crystals have a pseudoquadratic rhombo-hedral form. Crystals of hemerythrin from Sipunculus nudus show considerable polymorphism, but most are orthorhombic (Roche, 1935). 

Except for the iron content, chemical analysis has only been performed on hemerythrin from Sipunculus. Leaving aside the results of Griffiths (1892a) and Cuenot (1900) because the preparations used cannot have been pure, the only data existing in the literature is that of Roche (1934, 1935). (See Table II.)... 

The Ei.ementary Composition of Hemerythrin FROM Sipunculus nudus ... 

The number of iron atoms per molecule (calculated on the basis of the largest analytical values found) is 10 for the hemerythrin from Sipunculus and 19 for that of Phascolosoma. 

Only hemerythrin from Sipunculus nudus has been examined for amino acid content. Apart from the old percentage data of Roche (1934)... 

Until determinations of the iron-oxygen ratio of hemerythrins from different species are performed under strictly determined conditions and using the same methods, it is difficult to believe that the discrepancies appearing between Sipunculus and Phascolosoma for such a fundamental property can only be caused by the different origins of the biological material. 

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