Pigments haeme

Pyrrole occurs in bone oil and imparts a bright red colour to pine wood moistened with mineral acid this characteristic behaviour led to its discovery and is used as a qualitative test for pyrrole derivatives. The bile pigments are metabolic products having chains of four pyrrole rings. Their precursors are porphyrins, which include the blood pigments (haem), the chlorophylls, and vitamin B12, and consist of four pyrrole units joined in a macro ring (Section 2.3.1.2). The trisubstituted pyrrole 6 (porphobilinogen) is the biosynthetic precursor of haem and chlorophyll. 

The most common structures of this type are the 2,5-exo derivatives 51 of which common examples are maleimide 53, phthalimide 54, maleic anhydride 55, and phthalic anhydride 56. The structural unit 51 occurs widely and more complex examples are the blood pigment haem 57 and the synthetic phthalocyanine dyes, e.g., 58. 

Chromoproteins. Compounds of proteins with haem or some similar pigments. 

Bilirubin and other pigments resulting from haem catabolism,... 

One of the important properties of porphyrins is that they complex with divalent metals, the pyrrole nitrogens being ideally spaced to allow this. Of vital importance to life processes are the porphyrin derivatives chlorophyll and haem. Chlorophyll (actually a mixture of structurally similar porphyrins chlorophyll a is shown) contains magnesium, and is, of course, the light-gathering pigment in plants that permits photosynthesis. 

Physiologically iron entering the developing erythrocyte is transferred to the mitochondrion where it is incorporated into a tetrapyrole synthesized from amino acids to form haem. This complex then returns to the cytoplasm where it is inserted into the globin molecule to make the red iron-transporting pigment called haemoglobin. 

Hornsey, H. C. (1956). The colour of cooked cured pork. 1. Estimation of the nitric oxide-haem pigments. J. Sci. FoodAgric. 7, 534-540. 

Walters, C. L., Casselden, R. J., and Taylor, A. M. (1967). Nitrite metabolism by skeletal muscle mitochondria in relation to haem pigments. Biochim. Biophys. Acta 143, 310-318. 

Krzywicki, K. 1982. The determination of haem pigments in meat. Meat Sci. 7 29-36. 

Warriss, P.D. 1979. The extraction of haem pigments from fresh meat. J. Food Technol. 14 75-80. 

Figure 48 Relative concentrations of total haem pigments in the dark muscle of cod during a 12-month period. The ordinate is the mean optical density at 512 nm of a 4-cm light path.

P2. Perryman, P. W., Richards, D. H., and Holbrook, B., Simultaneous microdetermination of serum bilirubin and serum haem-pigments. Biochem. J. 66, 61P (1957)... 

Similar reactions occur in red algae and cyanobacteria but because the full spectrum of sunlight does not always penetrate very far below the surface of the sea they make use of different pigments. These may be structurally similar to those used by plants, and are therefore classed as bacteriochlorophylls, or belong to the structurally distinct phycobilin class of compounds. Unlike chlorophyll, which has a cyclic tetrapyrrole structure containing magnesium, the phycobilins are acyclic tetrapyrroles with similarities to the breakdown product of the haem ring, bilirubin. 

Erythrocytes are produced in the red bone marrow and survive in the circulation for approximately 120 days. Old or abnormal red cells are destroyed by the reticulendothelial system and the products recycled. The amino acids liberated enter the liver haem is broken down to ferrous iron and the pigment bilirubin. Iron is stored as ferritin in tissues, and bilirubin is excreted in bile as a glucuronide. 

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