Hemes and chlorophylls

Biosynthesis of The starting point for heme and chlorophyll synthesis is aminolaevulinic acid 

Related topics Myoglobin and hemoglobin (B4) Photosynthesis (L3) Electron transport and oxidative Amino acid metabolism (M2) phosphorylation (L2) 

Tetrapyrroles The red heme and green chlorophyll pigments, so important in the energy- 

Hemes (Fig. la) are a diverse group of tetrapyrrole pigments, being present as the prosthetic group of both the globins (hemoglobin and myoglobin Topic 

Instant Notes in Biochemistry 2nd Edition, B.D. Hames N.M. Hooper, (c) 2000 BIOS Scientific Publishers Ltd, Oxford. 

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Some of the important types of coordination compounds occur in biological systems (for example, heme and chlorophyll). There are also significant applications of coordination compounds that involve their use as catalysts. The formation of coordination compounds provides the basis for several techniques in analytical chemistry. Because of the relevance of this area, an understanding of the basic theories and principles of coordination chemistry is essential for work in many related fields of chemistry. In the next few chapters, an introduction will be given to the basic principles of the chemistry of coordination compounds. 

Induced Circular Dichroism of Heme and Chlorophyll Bound to Proteins... 

The importance of phthalocyanines, apart from their early use as models for hemes and chlorophylls, lies in the fact that metal complexes of the phthalocyanine system produce extremely intense and useful dyestuffs. Much research has therefore been devoted to physical and spectroscopic studies of these molecules (B-81MI30700). Phthalocyanines are extremely stable, are stable to light, and are insoluble in most solvents, so they are very useful dyestuffs. 

H. Dailey, Editor, The Biosynthesis of Heme and Chlorophylls (1990), McGraw-Hill (New York). An excellent reference on the chemistry and biochemistry of chlorophyll. 

Related topics Protein structure (B3) Hemes and chlorophylls (M4)... 

Fig. 2. Pathway of the synthesis of heme and chlorophyll, (a) Synthesis of porphobilinogen from glycine and succlnyl CoA (b) synthesis of protoporphyrin IX from porphobilinogen. A = CH2COOH, M = CH3, P = CH2CH2COOH.

Since the development of chelate chemistry has taken place almost wholly within the last three decades, the number of applications that have been found for this class of compounds is quite remarkable. Mail may not, however, take credit for the two most important uses of chelate compounds the use of the magnesium chelate, chlorophyll, as a catalyst for the incorporation of the hydrogen of water into plant systems and the use of the iron chelate, heme, as an oxygen carrier in human respiration. The ring system in both heme and chlorophyll is essentially that shown for copper porphyrin in Figure 22-4, but there are organic substituents on... 

Numerous types of important coordination compounds (such as heme and chlorophyll) occur in nature. Some coordination compounds are useful as a result of their ability to function as catalysts for industrially important processes. Also, the formation of coordination compounds is central to certain techniques in analytical chemistry. Accordingly, some understanding of the chemistry of coordination compounds is vital to students whose interests lie outside inorganic chemistry. Certainly, the field of coordination chemistry is much broader in its applicability than to just inorganic chemistry. 

The precursor for vitamin B12 synthesis is uroporphyrinogen 111, the common precursor for aU porphyrins, including heme and chlorophyll. Uroporphyrinogen III is synthesized by condensation between succinyl coenzyme A (CoA) and glycine to yield 5-aminolevulinic acid. Two molecules of (5-amino-levulinic acid then condense to form the pyrrole phorphobilinogen, and four molecules of porphobilinogen condense to yield uroporphobilinogen III. 

The first two of these compounds occur at sufficiently high concentrations in some crudes to enable production of them from petroleum. Benzonitrile has also been detected [6]. Much of the trace metal content of petroleums, in particular vanadium and nickel, is present in association with petroporphy-rins, which are polycyclic pyrroles closely related in structure to the hemes and chlorophylls. These materials are examples of the more complex nitrogen heterocycles to be found in petroleum. These particular heterocycles with their complexed metal atoms contribute much to our present knowledge of the original biogenesis of the petroleum hydrocarbons [6]. 

Figure 2. A comparison of heme and chlorophyll a. Bacteriochlorophyll differ from chlorophyll in that the exterior double bond of ring II is saturated as it is in ring IV.

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