Protoporphyrin chlorophyll from

Castelfranco PA, Walker CJ, Weinstein JD (1994) Biosynthetic studies on chlorophylls from protoporphyrin IX to protochlorophyllide. In The biosynthesis of the tetrapyrrole pigments (Ciba Foundation Symposium 180). Wiley, Chichester, pp 194-204 Castignetti D, Hollocher TC (1982) Nitrogen redox metabolism of a heterotrophic, nitrifying-denitrifying Alcaligenes sp. from soil. Appl Environ Microbiol 44 923-928... 

FIGURE 2.1.5 Biosynthesis steps of porphyrins from protoporphyrin IX to chlorophyll a. 

Fig. 2.16 Chlorophyll biosynthesis from protoporphyrin IX to magnesium protoporphyrin IX-13-methylpropionate.

Methylpheophorbide a itself can be formed from chlorophyll a by removal of the central magnesium ion and transesterification with methanol. Partial synthesis was also used for the preparation of heme d (63) (13, 60) along a multistep reaction sequence starting from protoporphyrin IX dimethylester (26). 

Protoporphyrin IX is a precursor for the biosynthesis of heme, chlorophyll, and cytochrome. Bile pigment is also derived from heme. The structure of bilirubin, the main component of this bile pigment, is shown [7]. Bilirubin is also a main component of the crude drug Go-Oh (bezoar, concave) prepared from the unhealthy calculus in the gallbladder or bile duct of cattle. Bezoar is an animal preparation used for detoxification, as an antipyretic, and as a cardiotonic. The biosynthesis of chlorophylls and bacte-riochlorophylls from protoporphyrin IX has been reviewed [8]. 

The open-chain tetrapyrrole chromophores of phycobiliproteins (Fig. 2) share a common biosynthetic pathway with heme and chlorophyll from 5-aminole-vulinate to protoporphyrin IX (a pathway also shared by phytochrome of higher plants). Each phycobilipro-tein consists of a- and 3-chains. The M, of these polypeptides varies among species, but the a-chain (M,... 

The biosynthetic chain of chlorophyll begins with the small building blocks, acetate and glycine molecules, which are part of the basic metabolic milieu. These small molecules are condensed in a series of n steps to form the complex molecule protoporphyrin. From protoporphyrin two classes of compounds are formed namely, the iron porphyrins or hemes and the magnesium porphyrins which give rise eventually to chlorophyll. According to this scheme, heme and chlorophyll are related to each other biochemically, since both arise from the same precursor molecule, protoporphyrin. 

Fig. 24. Summary of suggested biosynthetic pathways from protoporphyrin to chlorophyll.

FIGURE 117.4 The biosynthesis of various chlorophylls from the common precursor, protoporphyrin IX. 

Chlorophyll. The pathway of chlorophyll synthesis has been elucidated through biochemical genetic studies of Rhodobacter spheroides y]7 118a which produces bacteriochlorophyll, from studies of cyanobacteria,419 420 and from investigations of green algae and higher plants,421 which make chlorophyll a. The first step in the conversion of protoporphyrin IX into chlorophyll is the insertion of Mg2+ (Fig. 24-23, step a). 

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.

Heme is an iron- and nitrogen-containing porphyrin ring system synthesized from glycine and succinyl-CoA. Protoporphyrin IX, the precursor of heme, is also a precursor of the chlorophylls. 

Fig. 5. Photoreduction of Fast Red A(FRA) in aqueous solution by the polymer mono-, dinuclear chlorophylls a from (Sc), (26) and mono-, dinuclear protoporphyrine-IX (39), (27) in the presence of ascorbic acid (150 W xenon-lamp, 293 K)68, m. Absorbance of FRA (at 520 nm with substruction of that at irradiation time Ao) plotted against irradiation time.

The biosynthesis of chlorophylls diverges from that of heme at the metal insertion stage. Magnesium is inserted into protoporphyrin IX by a little-known enzyme, called magnesium chelatase, followed by esterification of the propionic acid side chain on C-13 by transfer of a methyl group from... 

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