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aminopropanol phosphate biosynthesis II

The biosynthesis of |FRAME:ADENOSYLCOBINAMIDE| from |FRAME:CPD-691| requires the attachment of an aminopropanol group to the propionate side chain of the corrin ring. Isotope studies with cultures of microorganisms that biosynthesize vitamin B12 have clearly shown that the amino group and carbon chain of this part of cobalamin are both derived from |FRAME: THR| |CITS: [13416277]|. Initial work suggested that |FRAME: 1-AMINO-PROPAN-2-OL| might be formed from L-threonine by sequential action of two separate enzymes, namely |FRAME: EC-| and |FRAME: EC-| |CITS: [4577583]|. These two enzymes have been purified from |FRAME: TAX-83333| and were shown to catalyze the proposed reactions in vitro |CITS: [359547]|. The second enzyme was later shown to be identical with glycerol dehydrogenase |CITS: [3920199]|. At the time, it was proposed that |FRAME: 1-AMINO-PROPAN-2-OL| is the substrate for the |FRAME: MONOMER-13228 CbiB| enzyme, originally proposed to convert |FRAME:CPD-691| to |FRAME:ADENOSYLCOBINAMIDE| |CITS: [9446573]|. Suprisingly, a few years later a |FRAME: TAX-90371| mutant blocked in |FRAME:1-AMINO-PROPAN-2-OL| biosynthesis was found to be not defective in either of these two enzymes. That observation lead to the discovery of an alternative pathway (see |FRAME: PWY-5443|). Characterization of the alternative pathway suggested that the actual substrate for the |FRAME: MONOMER-13228 CbiB| enzyme is the phosphorylated form, |FRAME: R-1-AMINOPROPAN-2-YL-PHOSPHATE|, and that the product of CbiB is |FRAME: ADENOSYLCOBINAMIDE-P| |CITS: [9446573]|. If indeed |FRAME: R-1-AMINOPROPAN-2-YL-PHOSPHATE| is the final propduct of this pathway, it requires the phosphorylation of |FRAME: 1-AMINO-PROPAN-2-OL| by an as-yet unidentified kinase. As this kinase has not been found yet, it is still not clear whether this pathway is important in vivo for cobalamine biosynthesis.

from BIOCYC source record: META_PWY-7378
Type: pathway
Taxonomic scope
conserved biosystem

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