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A new pathway for salvaging the coenzyme B12 precursor cobinamide in archaea requires cobinamide-phosphate synthase (CbiB) enzyme activity.

Abstract：

:The ability of archaea to salvage cobinamide has been under question because archaeal genomes lack orthologs to the bacterial nucleoside triphosphate:5'-deoxycobinamide kinase enzyme (cobU in Salmonella enterica). The latter activity is required for cobinamide salvaging in bacteria. This paper reports evidence that archaea salvage cobinamide from the environment by using a pathway different from the one used by bacteria. These studies demanded the functional characterization of two genes whose putative function had been annotated based solely on their homology to the bacterial genes encoding adenosylcobyric acid and adenosylcobinamide-phosphate synthases (cbiP and cbiB, respectively) of S. enterica. A cbiP mutant strain of the archaeon Halobacterium sp. strain NRC-1 was auxotrophic for adenosylcobyric acid, a known intermediate of the de novo cobamide biosynthesis pathway, but efficiently salvaged cobinamide from the environment, suggesting the existence of a salvaging pathway in this archaeon. A cbiB mutant strain of Halobacterium was auxotrophic for adenosylcobinamide-GDP, a known de novo intermediate, and did not salvage cobinamide. The results of the nutritional analyses of the cbiP and cbiB mutants suggested that the entry point for cobinamide salvaging is adenosylcobyric acid. The data are consistent with a salvaging pathway for cobinamide in which an amidohydrolase enzyme cleaves off the aminopropanol moiety of adenosylcobinamide to yield adenosylcobyric acid, which is converted by the adenosylcobinamide-phosphate synthase enzyme to adenosylcobinamide-phosphate, a known intermediate of the de novo biosynthetic pathway. The existence of an adenosylcobinamide amidohydrolase enzyme would explain the lack of an adenosylcobinamide kinase in archaea.

journal_name

J Bacteriol

journal_title

Journal of bacteriology

authors

Woodson JD,Zayas CL,Escalante-Semerena JC

doi

10.1128/jb.185.24.7193-7201.2003

keywords:

subject

Has Abstract

pub_date

2003-12-01 00:00:00

pages

7193-201

issue

eissn

0021-9193

issn

1098-5530

journal_volume

185

pub_type

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A new pathway for salvaging the coenzyme B12 precursor cobinamide in archaea requires cobinamide-phosphate synthase (CbiB) enzyme activity.