Corrin

CRN

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Corrin is a heterocyclic ring system, related to the porphyrin ring of hemoglobin. It consists of four reduced pyrrole subunits ( tetrapyrrole ), which on three sides each have a-C ( CH ) = methine bridge and are connected directly to a page. Compared with porphyrin thus missing a methine bridge between two pyrroles.

The corrin ring structure is the central component in the cobalt -containing vitamin B12 ( cyanocobalamin ). It has properties similar to the aromatic 18π - porphyrin, however,

• More flexible,
• Not as smooth as porphyrin and
• Has a missing methine bridge and lack of double bonds do not have aromatic properties.

Corrinoids

Compounds containing a corrin backbone corrinoids may be mentioned. Almost all natural metal-containing corrinoids contain a central cobalt atom, whereas the related porphyrins may contain various metals ( such as platinum, nickel, cobalt, copper, iron, zinc, and magnesium). From phototrophic bacteria, metal-free corrinoids were isolated. Corrinoids are only produced by microorganisms.

Biosynthesis

The genus Propionibacterium synthesized various corrinoids from 5-aminolevulinic acid (5- ALA). This is dimerized to porphobilinogen ( PBG). PGB four units are on different Uroporphyrinogenen ( UPG I, II, III) connected to be methylated by means of the enzyme uroporphyrinogen III methyltransferase. Thereafter formed in a chain of approximately 30 reaction steps from a biologically active UPG corrinoid as z.Bsp. the cobalamin. Many higher organisms such as vertebrates, some mollusks, and crustaceans and insects synthesize a few in a similar way the structurally related, but iron instead of cobalt -containing hemoglobin; they lack the ability to remove the methine bridge between the two in corrinoids directly connected pyrrole subunits.