Escherichia coli membrane D-lactate dehydrogenase. Isolation of the enzyme in aggregated from and its activation by Triton X-100 and phospholipids.
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.
D002462:Cell Membrane / Q000201:enzymology; D002793:Cholic Acids / Q000494:pharmacology; D003840:Deoxycholic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000302:isolation & purification / Q000378:metabolism; D046911:Macromolecular Substances; D010743:Phospholipids / Q000494:pharmacology*; D011092:Polyethylene Glycols / Q000494:pharmacology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D013997:Time Factors
D002793:Cholic Acids; D046911:Macromolecular Substances; D010743:Phospholipids; D000644:Quaternary Ammonium Compounds; D003840:Deoxycholic Acid; D011092:Polyethylene Glycols; D007770:L-Lactate Dehydrogenase