title: Quarternary structure and enzymological properties of the different hormone-sensitive lipase (HSL) isoforms.
abstract: BACKGROUND
  Hormone-sensitive lipase (HSL) is a key enzyme in the mobilization of energy in the form of fatty acids from intracellular stores of neutral lipids. The enzyme has been shown to exist in different isoforms with different molecular masses (84 kDa, 89 kDa and 117 kDa) expressed in a tissue-dependent manner, where the predominant 84 kDa form in adipocytes is the most extensively studied.
  
  
  RESULTS
  In this study we employed negative stain electron microscopy (EM) to analyze the quarternary structure of the different HSL isoforms. The results show that all three isoforms adopt a head-to-head homodimeric organization, where each monomer contains two structural domains. We also used enzymatic assays to show that despite the variation in the size of the N-terminal domain all three isoforms exhibit similar enzymological properties with regard to psychrotolerance and protein kinase A (PKA)-mediated phosphorylation and activation.
  
  
  CONCLUSIONS
  We present the first data on the quaternary structure and domain organization of the three HSL isoforms. We conclude that despite large differences in the size of the N-terminal, non-catalytic domain all three HSL isoforms exhibit the same three-dimensional architecture. Furthermore, the three HSL isoforms are very similar with regard to two unique enzymological characteristics of HSL, i.e., cold adaptation and PKA-mediated activation.
authors.affiliation: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors.forename: Christian
authors.initials: C
authors.lastname: Krintel
authors.forename: Cecilia
authors.initials: C
authors.lastname: Klint
authors.forename: Håkan
authors.initials: H
authors.lastname: Lindvall
authors.forename: Matthias
authors.initials: M
authors.lastname: Mörgelin
authors.forename: Cecilia
authors.initials: C
authors.lastname: Holm
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D003080:Cold Temperature; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D020836:Protein Structure, Quaternary; D002787:Sterol Esterase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D007527:Isoenzymes; D017868:Cyclic AMP-Dependent Protein Kinases; D002787:Sterol Esterase