Haeme derivatives

Many heterocyclic compounds are biosynthesized by plants and animals and are biologically active. Over millions of years these organisms have been under intense evolutionary pressure, and their metabolites may be used to advantage for example, as toxins to ward off predators, or as colouring agents to attract mates or pollinating insects. Some heterocycles are fundamental to life, such as haem derivatives in blood and the... 

Among the anaerobic transelectronases containing haem derivatives are the cytochromes, described on page 119. 

Prepared by heating ammonium mucate, or from butyne-l,4-diol and ammonia in the presence of an alumina catalyst. The pyrrole molecule is aromatic in character. It is not basic and the imino-hydrogen atom can be replaced by potassium. Many pyrrole derivatives occur naturally, e.g. proline, indican, haem and chlorophyll. 

The whole process of chlorophyll disappearance in vascular plants is a complex multistep pathway, much as chlorophyll biosynthesis is, but for didactic reasons it can be abbreviated into two main stages. The first group of reactions produces greenish derivatives while the more advanced steps produce colorless compounds by an oxidative ring opening, analog to the oxygenolytic rupmre of the porphynoid macrocycle of haem. It is a very rapid process and despite considerable efforts, the detection of intermediates is difficult. ... 

Haemoglobin-derived haem iron has multiple pro-inflammatory effects resulting from its ability to initiate decomposition of lipid hydroperoxides from PUFAs. In... 

Like many vitamins, cobalamin is functionally active as a derived coenzyme, coenzyme B12. Structurally, this is composed of a corrin ring a haem-like porphyrin ring containing cobalt (Co3+) at the centre held by four coordination bonds. The fifth... 

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