title: Biosynthesis in Escherichia coli of sn-glycerol 3-phosphate, a precursor of phospholipid. Palmitoyl-CoA inhibition of the biosynthetic sn-glycerol-3-phosphate dehydrogenase.
abstract: Homogeneous biosynthetic sn-glycerol-3-phosphate dehydrogenase (EC 1.1.1.8) of Escherichia coli was potently inhibited by palmitoyl-CoA and other long chain acyl-CoA thioesters. The concentration dependence of this inhibition was not cooperative. Enzyme activity was inhibited 50% at 1 microM palmitoyl-CoA; thus, this inhibition occurred at concentrations below the critical micellar concentration of palmitoyl-CoA. Palmitoyl-CoA was a reversible, noncompetitive inhibitor with respect to both NADPH and dihydroxyacetone phosphate. Palmitoyl-CoA did not affect the quaternary structure of the enzyme. This inhibition could be prevented or reversed by the addition of phospholipid vesicles prepared from E. coli phospholipids. Palmitoyl-CoA did not alter the kinetics of inhibition by sn-glycerol 3-phosphate, which is a proven physiological regulator of this enzyme. Decanoyl-CoA, dodecanoyl-CoA, myristoyl-CoA, palmitoyl-(1,N6-etheno)CoA, stearoyl-CoA, and oleoyl-CoA inhibited sn-glycerol-3-phosphate dehydrogenase at concentrations below their critical micellar concentrations. Palmitate inhibited sn-glycerol-3-phosphate dehydrogenase activity 50% at 200 microM. Palmitoyl-carnitine, deoxycholate, taurocholate, and dodecyl sulfate were more potent inhibitors than Triton X-100, Tween-20, or Tween-80. Palmitoyl-acyl carrier protein at concentrations up to 50 microM had no effect on sn-glycerol-3-phosphate dehydrogenase activity. The possible physiological role of long chain fatty acyl-CoA thioesters in the regulation of sn-glycerol 3-phosphate and phospholipid biosynthesis in E. coli is discussed.
mesh_terms: D000214:Acyl Coenzyme A / Q000494:pharmacology*; D004926:Escherichia coli / Q000201:enzymology*; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism*; D005994:Glycerophosphates / Q000096:biosynthesis*; D007700:Kinetics; D010171:Palmitoyl Coenzyme A / Q000494:pharmacology*; D010743:Phospholipids / Q000096:biosynthesis*; D013329:Structure-Activity Relationship; D013501:Surface-Active Agents / Q000494:pharmacology
chemical_list: D000214:Acyl Coenzyme A; D005994:Glycerophosphates; D010743:Phospholipids; D013501:Surface-Active Agents; D010171:Palmitoyl Coenzyme A; D005993:Glycerolphosphate Dehydrogenase