Muscle respiratory pigments

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). 

From the nutritional point of view, haem pigments are of considerable importance in the supply of iron to the human organism. The so-caUed haem iron, which includes iron bound in myoglobin and haemoglobin and iron bound in muscle respiratory enzymes, is absorbed in the body at a level of 10-30%, whQe non-haem iron from only 1-5%. 

Flower pigments of the East African koso tree Hage-nia abyssinica (Rosaceae), occurring in the plant as a mixture of a-K. (C25H32O8, Mr 460.52, yellow needles, mp. 160°C), and K. (C25HJ2O, Mr 460.52, mp. 120°C). K. are the decomposition products of the so-called koso toxin and prototoxin. These compounds are muscle toxins for lower animals. Koso also has a muscle-paralysing effect in warm-blooded animals and causes death by respiratory paralysis. In humans, local irritations of the gastrointestinal tract, visual disorders, and severe states of collapse have been observed. K. slows cardiac activity. It is used as an anthelminthic. 

---