Membrane-bound lactate dehydrogenases and mandelate dehydrogenases of Acinetobacter calcoaceticus. Location and regulation of expression

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Abstract
A. calcoaceticus possesses an L(+)-lactate dehydrogenase and a D(-)-lactate dehydrogenase. Results of experiments in which enzyme activities were measured after growth of bacteria in different media indicated that the 2 enzymes were co-ordinately induced by either enantiomer of lactate but not by pyruvate, and repressed by succinate or L-glutamate. The 2 lactate dehydrogenases have very similar properties to L(+)-mandelate dehydrogenase and D(-)-mandelate dehydrogenase. All 4 enzymes are NAD(P)-independent and were integral components of the cytoplasmic membrane. The enzymes could be solubilized in active form by detergents; Triton X-100 or Lubrol PX were particularly effective. D(-)-Lactate dehydrogenase and D(-)-mandelate dehydrogenase could be selectively solubilized by the ionic detergents cholate, deoxycholate and sodium dodecyl sulfate.