title: Crotonobetaine reductase from Escherichia coli--a new inducible enzyme of anaerobic metabolization of L(-)-carnitine.
abstract: Crotonobetaine reductase from Escherichia coli 044 K74 is an inducible enzyme detectable only in cells grown anaerobically in the presence of L(-)-carnitine or crotonobetaine as inducers. Enzyme activity was not detected in cells cultivated in the presence of inducer plus glucose, nitrate, gamma-butyrobetaine or oxygen, respectively. Fumarate caused an additional stimulation of growth and an increased expression of crotonobetaine reductase. The reaction product, gamma-butyrobetaine, was identified by autoradiography. Crotonobetaine reductase is localized in the cytoplasm, and has been characterized with respect to pH (pH 7.8) and temperature optimum (40-45 degrees C). The Km value for crotonobetaine was determined to be 1.1 x 10(-2M). gamma-Butyrobetaine, D(+)-carnitine and choline are inhibitors of crotonobetaine reduction. For gamma-butyrobetaine (Ki = 3 x 10(-5M)) a competitive inhibition type was determined. Various properties suggest that crotonobetaine reductase is different from other reductases of anaerobic respiration.
authors.affiliation: Department of Biochemistry, University of Leipzig, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Roth
authors.forename: K
authors.initials: K
authors.lastname: Jung
authors.forename: H
authors.initials: H
authors.lastname: Jung
authors.forename: R K
authors.initials: RK
authors.lastname: Hommel
authors.forename: H P
authors.initials: HP
authors.lastname: Kleber
mesh_terms: D000693:Anaerobiosis; D002331:Carnitine / Q000378:metabolism*; D002474:Cell-Free System; D004926:Escherichia coli / Q000201:enzymology*; D009097:Multienzyme Complexes; D010088:Oxidoreductases / Q000032:analysis*
chemical_list: D009097:Multienzyme Complexes; D010088:Oxidoreductases; C067153:crotonobetaine reductase; D002331:Carnitine