Abstract
Human hepatic lipase is an important enzyme in high density lipoprotein (HDL) metabolism, being implicated in the conversion of HDL2 to HDL3. Three human hepatic lipase cDNA clones were identified in two lambda gt11 libraries from human liver. The cDNA-derived amino acid sequence predicts a protein of 476 amino acid residues, preceded by a 23-residue signal peptide. Four potential N-glycosylation sites are identified, two of which are conserved in rat hepatic lipase. On alignment with human, mouse, and bovine lipoprotein lipase, the same two sites were also conserved in lipoprotein lipase in all three species. Stringent conservation of the cysteine residues was also evident. Comparative analysis of amino acid sequences shows that hepatic lipase evolves at a rapid rate, 2.07 x 10(-9) substitutions/site/year, about four times that in lipoprotein lipase and half that in pancreatic lipase. Further, hepatic lipase and pancreatic lipase appear to be evolutionarily closer to each other than either of them is to lipoprotein lipase. Southern blot analysis revealed high frequency restriction fragment length polymorphisms of the hepatic lipase gene for the enzymes HindIII and MspI. these polymorphisms will be useful for haplotype and linkage analysis of the hepatic lipase gene. Using cloned human hepatic lipase cDNA as a hybridization probe, we performed Southern blot analysis of a panel of 13 human-rodent somatic cell hybrids. Concordance analysis of the various hybrid clones indicates that the hepatic lipase gene is located on the long arm of human chromosome 15. Analysis of hybrids containing different translocations of chromosome 15 localized the gene to the region 15q15----q22.
Highlights
3).Hepatectomy experiments implicate the liver as themain source of hepatic lipase in postheparin plasma [4].Direct evidence for the production of hepatic lipase has been demonstrated in liver parenchymal cells [5,6,7]
Human Hepatic Lipase cDNA Sequence berof amino acid substitutions between homologous protein sequences is estimated by Kimura's method [22], which makes a correction for multiple substitutions at the same residue site
Human Hepatic Lipase cDNA and DeducedAminoAcid Sequence-The complete sequence of human hepatic lipase cDNA is deduced from three overlapping clones (Fig. 1).Both strands were sequenced in entirety, and all restriction sites were crossed
Summary
Hepatic lipase catalyzes the hydrolysis of tri-, di-, and monoacylglycerol, acyl-CoAthioesters, and phospholipids Comparative lipase cDNA clone was identified in a rat liver cDNA library in Xgtll analysis of amino acid sequences shows that hepatic lipase evolves at a rapid rate,2.07 X lo-*substitutions/. Three overlapping human hepatic lipase cDNA clones were identified and confirmed by complete sequencing using lipase and pancreatic lipase appeabre etovolutionarily the chain terminationmethod of Sanger et al [17] followingsubcloncloser to each other than eitheorf them is to lipoprotein ing in the M13 vectors mp and mp. LS-6 isa human-mouse hybrid constructed from a patient with Prader-Willi syndrome and a balanced translocation 45, XX,-15,-17,+der(l7)t(l$l7)(ql3;p13) (case reported by Elder et al. The nucleatidesequence(.) reported in this paperhas been submitted I The abbreviations used are: IDL, intermediate density lipoproto the GenBankTM/EMBL Data Bank withaccessionnumber(s) teins; HDL, high density lipoproteins; RFLP, restriction fragment length polymorphism; kb, kilobase pair(s). Human Hepatic Lipase cDNA Sequence berof amino acid substitutions between homologous protein sequences is estimated by Kimura's method [22], which makes a correction for multiple substitutions at the same residue site
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