Effects of bovine serum albumin and phospholipids on activity of microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase in sweet potato roots

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Sweet potato microsomal 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase preincubated at 30℃ was inactivated 50 to 60%. The inactivation depended on temperature and was much less with preincubation below 20℃. High concentration (above 0.6% w/v) of bovine serum albumin not only prevented inactivation but also increased the activity. Even after preincubation for a given time without bovine serum albumin, its addition at 1% (w/v) prevented inactivation during further incubation, although it was unable to restore the. activity to the initial level. Microsomal lipids were hydrolyzed during preincubation at 30℃. There was a positive correlation between formation of fatty acids during the preincubation and loss of HMG-CoA reductase activity. The micelles prepared from sweet potato microsomal phospholipids also prevented enzyme inactivation. These results suggest that the hydrolysis of microsomal phospholipids induces the instability of microsomal HMG-CoA reductase by altering microsomal membrane structures and that the enzyme requires phospholipids for its activity. Besides bovine serum albumin and phospholipids, NADPH_2 and HMG-CoA added together prevented inactivation of this enzyme but not when added separately.
日本植物生理学会の論文