Crotonobetaine reductase from Escherichia coli--a new inducible enzyme of anaerobic metabolization of L(-)-carnitine.
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.
Roth
S
S
Department of Biochemistry, University of Leipzig, Germany.
Jung
K
K
Jung
H
H
Hommel
R K
RK
Kleber
H P
HP
D000693:Anaerobiosis; D002331:Carnitine / Q000378:metabolism*; D002474:Cell-Free System; D004926:Escherichia coli / Q000201:enzymology*; D009097:Multienzyme Complexes; D010088:Oxidoreductases / Q000032:analysis*
D009097:Multienzyme Complexes; D010088:Oxidoreductases; C067153:crotonobetaine reductase; D002331:Carnitine