32] Phospholipase activity of milk lipoprotein lipase

Abstract

Publisher Summary This chapter describes various methods to prepare and handle milk lipoprotein lipase (LpL) and its activator protein and conditions required to be considered in kinetic studies. Bovine milk contains 1–2 mg active LpL per liter, and the enzyme can be purified by simple methods in yields approaching 50%. This has made LpL from bovine milk the most used model enzyme in LpL research. In the lactating mammary gland, LpL has an important role for uptake of lipids from plasma lipoproteins. All the methods to prepare LpL from milk are based on chromatography on heparin-Sepharose, with some different additional steps. The chapter presents a simple method suitable for preparation of LpL for kinetic studies. LpL is also sometimes defined as the salt-sensitive lipase. The enzyme can exert full catalytic activity even in the presence of 1 M NaCl. The effect of salt is not exerted at this level but on the physical state and the stability of the enzyme molecule. For most purposes, NaCl concentrations of 0.05–0.15 M result in optimal activity and stability for kinetic studies.