title: Hydrolysis of glyceryl tri(1- 14 C)octanoate and glyceryl tri(1- 14 C)oleate monolayers by postheparin lipolytic activity.
abstract: The hydrolysis of monomolecular films of glyceryl tri[1-(14)C]octanoate and glyceryl tri[1-(14)C]oleate has been demonstrated by measurement of the decrease in surface radio-activity that occurs in the presence of postheparin plasma. The hydrolysis displayed first order kinetics and was proportional to enzyme concentration over a 10-fold range. No hydrolysis was observed in the absence of enzyme, and only slight activity (1%) was found in plasma taken from subjects before heparin administration. The hydrolysis was stimulated to a variable extent by Ca(2+). The first product of hydrolysis of the monolayer was identified as 1,2-diglyceride, which was subsequently converted to 2-monoglyceride. Inhibition of triglyceride hydrolysis was observed when postheparin plasma was preincubated in 2 m NaCl, 10(-4) m protamine, 10 mm Na(4)P(2)O(7), and 0.1 m NaF. Monolayer techniques avoid some but not all of the problems associated with emulsified lipid substrates and appear to be applicable for study of post-heparin lipolytic activities.
mesh_terms: D002247:Carbon Isotopes; D004655:Emulsions; D005227:Fatty Acids; D005990:Glycerol; D006493:Heparin; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008071:Lipoprotein Lipase / Q000097:blood; D008567:Membranes, Artificial; D009829:Oleic Acids; D014304:Triolein
chemical_list: D002247:Carbon Isotopes; D004655:Emulsions; D005227:Fatty Acids; D008567:Membranes, Artificial; D009829:Oleic Acids; D014304:Triolein; D006493:Heparin; D008071:Lipoprotein Lipase; D005990:Glycerol