The Anaerobic Pathway was worked out in Pseudomonas denitrificans in a collaborative effort between geneticists and biochemists at Rhone-Poulenc and chemists at Cambridge University, primarily in the lab of Professor Sir Allan Battersby. Five clones bearing cobalamin biosynthetic genes have been sequenced from this organism:

• cobEABCD
• cobFGHIJKLM
• cobNOPQW
• cobVU
• cobXST

The reaction sequence shown below is still speculative. In particular, the addition of 1-amino-2-propanol-phosphate and DMB-Ribose have not been authenticated.

Step	Chemical Structure	Reactions	Salmonella Enzyme
1		Methylation at C2 CobA	CysG
2		Methylation at C7 CobA	CysG
3		Methylation at C20 CobI	CbiL
4		Reduction and Lactone Formation CobG
5		Methylation at C17 CobJ	CbiH
6		Spontaneous Ring Contraction
7		Methylation at C11 CobM	CbiF
8		Acetate Extrusion CobM	CbiF?
9		Methylation at C1 CobF	??
10		Ring Reduction CobK	??
11		Methylation at C15 CobL (N)	CbiE
12		Methylation at C5 CobL (N)	CbiE
13		Decarboxylation CobL (C)	CbiT
14		Methyl Migration CobH	CbiC
15		a,c - Amidations CobB	CbiA
16		Cobalt Insertion CobN,S,T	CysG or CobK
17		Cobalt Reduction ??	??
18		Adenosylation CobO	CobA
19		b, d, e, g Amidations CobQ	CbiP
20		Aminopropanol Addition CobC	CbiB
21		Guanidylation CobP	CobU
22		DMB Addition CobV	CobS
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Last Updated 14 August 2006, by JG Lawrence