SEPARATION AND CHARACTERIZATION OF THE ACID LIPASE AND NEUTRAL ESTERASES FROM HUMAN-LIVER

  • 1 January 1980
    • journal article
    • research article
    • Vol. 32  (6) , 869-879
Abstract
Electrophoresis of human liver homogenates followed by reaction with 4-methylumbelliferyl palmitate reveals the presence of 2 major electrophoretic forms with esterase (lipase) activity toward this substrate. The 2 enzymes were isolated and partially purified based on their solubility differences and their relative affinities for the lectin column concanavalin A-Sepharose 4B. Lipase A was particulate with an acidic pH optimum (5.2) and could be solubilized with the non-ionic surfactant Triton X-100. Lipase B was soluble and had a more neutral pH optimum (6.3-6.6). Both forms bound to immobilized concanavalin A and could be specifically eluted. Buffers containing .alpha.-methylmannoside eluted lipase B, and buffers with .alpha.-methylmannoside and Triton X-100 eluted lipase A, giving a 22- and 257-fold purification, respectively, over whole-tissue homogenates. Cholesterol oleate, trioleoylglycerol and 4-methylumbelliferyl palmitate were substrates for solubilized lipase A. Lipase B hydrolyzed 4-methylumbelliferyl palmitate but not trioleoylglycerol or cholesterol oleate. Lipase B was more thermolabile than lipase A, and it was selectively inhibited by diethyl-p-nitrophenyl phosphate at low concentrations. Apparently lipase A and B are distinctly different enzymes and are probably unrelated polymorphic forms of one another.

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