Effects of lipid removal on the molecular size and kinetic properties of bovine plasma arylesterase

Abstract

A purified arylesterase preparation from bovine plasma was characterized to the extent that it has a partial specific volume of 0.91ml/g and an apparent z-average molecular weight of 440000. The relatively large magnitude of the former reflects the presence of phospholipids, cholesterol, triglycerides and beta-carotene, the last-named being responsible for the pronounced yellow colour of the preparation. Removal of the lipid material is accompanied by a decrease in the apparent z-average molecular weight to 120000, the size of the smallest species detected by high-speed sedimentation equilibrium being in the vicinity of 70000 daltons: denaturation of the lipid-free preparation with 6m-guanidine hydrochloride caused essentially complete breakdown into subunits of this size. In kinetic studies on the enzyme the maximal velocity for the hydrolysis of phenyl acetate was found to increase by 60% on addition of 1 mm-Ca(2+), with the K(m) showing a concomitant decrease from 6.6 to 2.1 mm. Removal of lipid had no detectable effect on V(max.) or K(m) in either the presence or the absence of Ca(2+). It is concluded that the bovine plasma arylesterase preparation is either a lipoprotein or an enzyme-lipoprotein complex with properties very similar to those of the alpha(1)-lipoprotein or high-density lipoprotein (HDL(2)) fraction of serum.

Human Serum Paraoxonase/Arylesterase’s Retained Hydrophobic N -Terminal Leader Sequence Associates With HDLs by Binding Phospholipids

“…22,23,41 Phospholipid addition restores these activities. 22 We speculated that detergent induced the loss of activity resulting from phospholipid removal from PON1's N-terminus.…”

Distribution Spectrum of Paraoxonase Activity in HDL Fractions

“…PON1 was initially assumed to be located in HDL 2 (arylesterase activity without eserin but with EDTA) (5,6 ) and later in HDL 3 (7 ), but these investigators provided no detailed information on the centrifugation procedure or on the distribution profile of PON1 in HDL subfractions. Other studies led to the postulate that PON1 activity measurement was suitable for quantification of HDL 3 , but this was confirmed only on the basis of polyethylene glycol precipitation (8,9 ).…”

Effects of Cumin Extract on oxLDL , Paraoxanase 1 Activity , FBS, Total Cholesterol , Triglycerides , HDL-C , LDL-C , Apo A1 , and Apo B in in the Patients with Hypercholesterolemia

“…All biochemical tests were measured in serum on BT 3000 automatic analyzer by commercial kits (Pars Azmoon, Iran). Arylesterase activity was measured using phenylacetate as the substrate according to the modified procedure of Kitchen et al (14) PON1 activity toward paraoxon was measured after the reaction of paraoxon hydrolysis into pnitrophenol and diethylphosphate catalyzed by the enzyme. (15) The oxLDL was measured by a sandwich ELISA method using commercial kit (Mercodia-Sweden).…”