Abstract
In this study the role of high density lipoproteins on the plasma LCAT reaction was reported. When the fresh plasma was filtered through Sephadex G200, the enzyme peak coincided with HDL which was shown by lecithin determination. The association of the enzyme with HDL was demonstrated by the determination of LCAT activity present in D=1.25 supernatant fraction which had been separated after the incubation of inactivated HDL with LCAT. ApoA-1, which is one of the two major apoproteins present in HDL, activated the LCAT reaction when lecithin: cholesterol emulsions were used as substrate. To investigate the mechanism of the activation of LCAT reaction by ApoA-1, apoHDL-Sepharose was prepared and was subsequently used for the binding with LCAT. The binding of the enzyme to apoHDL-Sepharose was almost negligible, however, weak but definite binding of LCAT to lecithin-apoA-Sepharose was shown.
The physiological significance of the plasma LCAT reaction remains to be disclosed. However, the fact that the plasma LCAT reaction is higher in hyperlipemic diabetics and in extreme obesity, supports some role of LCAT reaction on plasma triglyceride metabolism.
