Glycerolipid biosynthesis in rat adipose tissue. IX. Activation of diglyceride acyltransferase by spermine.

The effect of Z protein, bovine serum albumin and spermine on 1,2-diacylglycerol acyltransferase (DGAT) was investigated. DGAT was measured in the presence of [14C]-palmitoyl-CoA and 1,2-diacylglycerol dispersed in Tween 20. As noted earlier, the activation of DGAT was observed in the presence of either spermine or Mg2+, with spermine being more effective. Addition of bovine serum albumin or Z protein to the incubation mixture resulted in further increase in the activity of this enzyme. However, in the absence of spermine or Mg2+, these proteins were ineffective in the activation of this reaction. The activation of DGAT, either by spermine or Mg2+ was reversed in the presence of ATP. Hydrogen peroxide was inhibitory, while catalase had no effect on the activation of DGAT by spermine. These results suggest that the activation of DGAT by spermine may reside in its ability to preserve the membrane integrity of microsomal membranes, to maintain the optimal and noninhibitory levels of palmitoyl-CoA and to provide a cationic environment required for the optimal activity of this enzyme.