Characterization of a cytoplasmic trehalase of Escherichia coli.
J Bacteriol. 1996 Nov; 178(21):6250-7.JB

Abstract

Escherichia coli can synthesize trehalose in response to osmotic stress and is able to utilize trehalose as a carbon source. The pathway of trehalose utilization is different at low and high osmolarity. At high osmolarity, a periplasmic trehalase (TreA) is induced that hydrolyzes trehalose in the periplasm to glucose. Glucose is then taken up by the phosphotransferase system. At low osmolarity, trehalose is taken up by a trehalose-specific enzyme II of the phosphotransferase system as trehalose-6-phosphate and then is hydrolyzed to glucose and glucose-6-phosphate. Here we report a novel cytoplasmic trehalase that hydrolyzes trehalose to glucose. treF, the gene encoding this enzyme, was cloned under ara promoter control. The enzyme (TreF) was purified from extracts of an overexpressing strain and characterized biochemically. It is specific for trehalose exhibiting a Km of 1.9 mM and a Vmax of 54 micromol of trehalose hydrolyzed per min per mg of protein. The enzyme is monomeric, exhibits a broad pH optimum at 6.0, and shows no metal dependency. TreF has a molecular weight of 63,703 (549 amino acids) and is highly homologous to TreA. The nonidentical amino acids of TreF are more polar and more acidic than those of TreA. The expression of treF as studied by the expression of a chromosomal treF-lacZ fusion is weakly induced by high osmolarity of the medium and is partially dependent on RpoS, the stationary-phase sigma factor. Mutants producing 17-fold more TreF than does the wild type were isolated.

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ncbi.nlm.nih.gov
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Authors+Show Affiliations

Horlacher R
Department of Biology, University of Konstanz, Germany.
Uhland K
No affiliation info available
Klein W
No affiliation info available
Ehrmann M
No affiliation info available
Boos W
No affiliation info available

MeSH

Amino Acid SequenceBacterial ProteinsBase SequenceChromosomes, BacterialCytoplasmDNA, BacterialEscherichia coliLac OperonMolecular Sequence DataMutagenesis, InsertionalRecombinant Fusion ProteinsSequence Homology, Amino AcidSigma FactorTrehalaseTrehalose

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

8892826