Multiple forms of sheep serum A-esterase activity associated with the high-density lipoprotein

Abstract

Five lipoproteins of sheep serum expressing A-esterase activity, but with differing activities towards four organophosphate substrates, were separated by a combination of gel filtration and ion-exchange chromatography. Each had an Mr of approx. 360,000 and contained a major peptide of Mr 28,000-30,000 that appeared to be present as several isoforms on urea/agarose isoelectric focusing. In every case this peptide split into a number of bands on urea/agarose isoelectric focusing. The bands appear to represent isoforms of the peptide, and four lipoproteins yielded characteristic patterns of bands. This peptide resembles the apolipoprotein A-I of human serum, and available evidence suggests that this is the protein that expresses A-esterase activity. Evidence is presented for the existence of different species of high-density lipoprotein HDL2 particles containing different complements of peptide isoforms and expressing contrasting substrate specificities towards organophosphates.

Bovine Paraoxonase 1 Activities in Serum and Distribution in Lipoproteins

“…Mackness and Walker [18] presented evidence that arylesterase and paraoxonase activities of sheep serum were associated with different proteins. In bovine serum, there was a high correlation between arylesterase activity and paraoxonase activity (Fig.…”

Biochemical Parameters in Toxicological Studies in Africa

“…PON/arylesterase of human serum (PON1; EC 3.1.1.8) also known as aromatic esterase 1 or serum aryldialkylphosphatase, and of several other mammalian species catalyzes the hydrolysis of organophosphates, aromatic carboxylic acids, and possibly carbamates ( Figure 23.12). Human serum PON1 is a calciumdependent esterase and is closely associated with the HDL complex [77]. There is very little information available on PON2.…”

A review of paraoxonase 1 properties and diagnostic applications

“…PON1 is associated with the major HDL structural Apolipoprotein A-I (Apo A-I) (Mackness et al 1988). PON1 -Apo A-I binding occurs with high affinity and leads to increased enzyme stability.…”