Conversion of low density lipoprotein 1 (LDL1, 1.019 less than d less than 1.045) to low density lipoprotein 2 (LDL2, 1.045 less than d less than 1.063) by hepatic triglyceride lipase.

The role of lipoprotein lipase and hepatic lipase in the conversion of LDL1 (1.019 less than d less than 1.045) to LDL2 (1.045 less than 1.063) were investigated on the basis of incubation of 125I-LDL1 with postheparin plasma (PHP) at NaCl concentrations of both 0.15 M and 1.0 M. Insignificant small increments of radioactivity and apoprotein B specific activity of LDL2 were observed even when 125I-LDL1 was incubated with preheparin plasma as the control. When 125I-LDL1 was incubated with PHP, the LDL1 radioactivity decreased and the LDL2 radioactivity increased significantly. the apoprotein B specific activity was also increased in the LDL2 fraction. One molar NaCl did not inhibit these changes. It is concluded that hepatic triglyceride lipase was the major mediator in the conversion of LDL1 to LDL2.