Named vitamin B, this compound could be isolated as pure, red crystals from various animal and microbial sources, and the X-ray crystal structure of this complex molecule, one of the largest nonpolymeric natural compounds, was determined in the 1950s by Dorothy Hodgkin et al. The structural core of corrinoids is the corrin ring in which the central cobalt atom is coordinated by four pyrrole groups (Fig. The lower (α) axial ligand is attached to the corrin ring via the nucleotide loop which is characterized by an unusual α-glycosidic linkage to C-1 of the ribosyl moiety (30).The B biosynthetic pathway is characterized by two converging branches: the synthesis of the corrin ring and the synthesis and activation of the α-axial ligand (23, 30).The “aerobic” pathway requires oxygen and has been characterized in depth in biosynthetic enzymes is restricted to anaerobic or microaerobic conditions (22, 30).
In fact, a modification of that work that was introduced by Tishler was actually used for decades for the bulk production of the vitamin.
Over 50 years ago, a deadly autoimmune disease known as pernicious anemia, which is characterized by neurological and hematological abnormalities, had no known cure.
The isolation of the anti-pernicious anemia factor from liver extracts by Folkers and Smith in 1948 represented a breakthrough in the treatment of this disease (21, 25). Since that time, thousands of researchers have identified and characterized a variety of enzymes that utilize B-like compounds are collectively termed corrinoids. In the cofactor forms, the upper (β) axial ligand (R) consists of either 5′-deoxyadenosine or a methyl group, which facilitate radical or methyl transfer reactions, respectively (14).
All the genes and enzymes specific to the pathway have been characterized in plants, at least in (Ravanel et al. The pterin and p ABA moieties are first synthesized in separate branches of the pathway.
The synthesis of dihydropterin from GTP involves the enzymes GTP-cyclohydrolase I, dihydroneopterintriphosphate pyrophosphatase, and dihydroneopterin aldolase (reactions 1–3, Figure 2).