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Ethylmalonyl coenzyme A mutase operates as a metabolic control point in Methylobacterium extorquens AM1.

Abstract：

:The metabolism of one- and two-carbon compounds by the methylotrophic bacterium Methylobacterium extorquens AM1 involves high carbon flux through the ethylmalonyl coenzyme A (ethylmalonyl-CoA) pathway (EMC pathway). During growth on ethylamine, the EMC pathway operates as a linear pathway carrying the full assimilatory flux to produce glyoxylate, malate, and succinate. Assimilatory carbon enters the ethylmalonyl-CoA pathway directly as acetyl-CoA, bypassing pathways for formaldehyde oxidation/assimilation and the regulatory mechanisms controlling them, making ethylamine growth a useful condition to study the regulation of the EMC pathway. Wild-type M. extorquens cells were grown at steady state on a limiting concentration of succinate, and the growth substrate was then switched to ethylamine, a condition where the cell must make a sudden switch from utilizing the tricarboxylic acid (TCA) cycle to using the ethylmalonyl-CoA pathway for assimilation, which has been an effective strategy for identifying metabolic control points. A 9-h lag in growth was observed, during which butyryl-CoA, a degradation product of ethylmalonyl-CoA, accumulated, suggesting a metabolic imbalance. Ethylmalonyl-CoA mutase activity increased to a level sufficient for the observed growth rate at 9 h, which correlated with an upregulation of RNA transcripts for ecm and a decrease in the levels of ethylmalonyl-CoA. When the wild-type strain overexpressing ecm was tested with the same substrate switchover experiment, ethylmalonyl-CoA did not accumulate, growth resumed earlier, and, after a transient period of slow growth, the culture grew at a higher rate than that of the control. These findings demonstrate that ethylmalonyl-CoA mutase is a metabolic control point in the EMC pathway, expanding our understanding of its regulation.

journal_name

J Bacteriol

journal_title

Journal of bacteriology

authors

Good NM,Martinez-Gomez NC,Beck DA,Lidstrom ME

doi

10.1128/JB.02478-14

subject

Has Abstract

pub_date

2015-02-15 00:00:00

pages

727-35

issue

eissn

0021-9193

issn

1098-5530

pii

JB.02478-14

journal_volume

197

pub_type

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Ethylmalonyl coenzyme A mutase operates as a metabolic control point in Methylobacterium extorquens AM1.