Choline oxidase, a catabolic enzyme in Arthrobacter pascens, facilitates adaptation to osmotic stress in Escherichia coli

Abstract

Choline oxidase (EC 1.1.3.17) is a bifunctional enzyme that is capable of catalyzing glycine betaine biosynthesis from choline via betaine aldehyde. A gene (cox) encoding this enzyme in the gram-positive soil bacterium Arthrobacter pascens was isolated and characterized. This gene is contained within a 1.9-kb fragment that encodes a polypeptide of approximately 66 kDa. Transfer of this gene to an Escherichia coli mutant that is defective in betaine biosynthesis resulted in an osmotolerant phenotype. This phenotype was associated with the ability of the host to synthesize and assemble an enzymatically active choline oxidase that could catalyze biosynthesis of glycine betaine from an exogenous supply of choline. Although glycine betaine functions as an osmolyte in several different organisms, it was not found to have this role in A. pascens. Instead, both choline and glycine betaine were utilized as carbon sources. In A. pascens synthesis and activity of choline oxidase were modulated by carbon sources and were susceptible to catabolite repression. Thus, cox, a gene concerned with carbon utilization in A. pascens, was found to play a role in adaptation to an environmental stress in a heterologous organism. In addition to providing a possible means of manipulating osmotolerance in other organisms, the cox gene offers a model system for the study of choline oxidation, an important metabolic process in both procaryotes and eucaryotes.

Osmoregulation in Bacillus subtilis: synthesis of the osmoprotectant glycine betaine from exogenously provided choline

“…6B and C). Thus, B. subtilis uses exoge- 4,7,8,17,22,23,29). This oxidation is a two-step process with e as a precursor for glycine betaine synthesis.…”

Choline transport activity in Staphylococcus aureus induced by osmotic stress and low phosphate concentrations

“…Enzymes mediating the oxidation of choline to glycine betaine are also presumably induced by osmotic stress in S. aureus. However, different enzymes in different organisms may be involved in this pathway (14,18,20), and the pathway operating in S. aureus is not known.…”

Synthesis of the osmoprotectant glycine betaine in Bacillus subtilis: characterization of the gbsAB genes

“…The ability to synthesize glycine betaine from choline is found in many cells of microbial, plant, and animal origin, and three different enzymatic systems can effect this synthesis. In Arthrobacter pascens, Arthrobacter globiformis, and an Alcaligenes sp., a bifunctional soluble choline oxidase that catalyzes the oxidation of choline and glycine betaine aldehyde to glycine betaine with the concomitant consumption of oxygen and the production of hydrogen peroxide has been found (23,40,47). In plants, glycine betaine synthesis occurs primarily in the chloroplasts and involves a soluble choline monooxygenase in combination with a soluble betaine aldehyde dehydrogenase (6,36,53).…”