Escherichia coli membrane D-lactate dehydrogenase. Isolation of the enzyme in aggregated form and its activation by Triton X-100 and phospholipids.:Isolation of the Enzyme in Aggregated Form and Its Activation by Triton X-100 and Phospholipids

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Description

D-Lactate dehydrogenase was obtained in an aggregated form consisting of 2 to 3 molecules of the monomer enzyme after removal of most Triton X-100 from the preparation as described previously (1). The aggregate dissociated reversibly to the monomeric form after addition of 0.06% or 1.0% Triton X-100. Formation of these aggregates was confirmed by the finding that the enzyme activity was only partially sensitive to specific antibody. The specific activity of the aggregated enzyme was one-third that of the enzyme with Triton X-100 and it increased approximately 5-fold on addition of phospholipids or cardiolipin of Escherichia coli and lecithin from egg yolk. Both the monomer and micelle forms of Triton X-100 caused activation of the enzyme. The activity of the aggregates after preincubation with Triton X-100 or phospholipids was completely inhibited by specific antibody. The difference in the properties of the aggregated enzyme after preincubation with Triton X-100 and with phospholipids suggested that its interaction with phospholipids was stronger than with Triton X-100. Kinetic studies also suggested a difference between the interactions of the enzyme with phospholipids and with Triton X-100. Aggregated enzyme had an apparent Km value for D-lactate similar to that of membrane-bound enzyme after preincubation with phospholipids.

Journal

  • J Biochem (Tokyo)

    J Biochem (Tokyo) 80 (4), 821-830, 1976

    The Japanese Biochemical Society

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