Lipoprotein lipase (LPL; triacylglycero-protein acylhydrolase, EC 3.1.1.34) was purified from bovine milk. Synthetic oligonucleotides were prepared, based on the amino acid sequences of three peptides obtained from partial digestion of purified LPL, and were used as probes to isolate cDNA clones for LPL mRNA from a bovine mammary gland.One of the clones, pLPL-49R2, contains an insert cDNA (49R2) of about 3.2 kilobases (kb) that hybridizes to all three probes and encodes a polypeptide that includes the NH2-terminal sequence of bovine LPL reported recently [Ben-Avram, C. M., Ben-Zeev, O., Lee, T. D., Hagga, K., Shively, J. E., Goers, J., Pedersen, M. E., Reeve, J. R. & Schotz, M. C. (1986) Proc.Nati. Acad. Sci. USA 83,[4185][4186][4187][4188][4189]. Complete nucleotide sequence analysis revealed that cDNA insert 49R2 contains the entire coding region for LPL as well as a 3' untranslated region of about 1.6 kb. The predicted amino acid sequence indicates that bovine LPL is a hydrophilic protein consisting of 450 amino acids (Mr 50,548) in its unglycosylated form. Blot hybridization analysis of poly(A)+ mRNA from bovine mammary gland demonstrated that there are at least three sizes of LPL mRNAs-3.2, 2.5, and 1.7 kb-with the 2.5-kb mRNA being the most abundant. Restriction endonuclease mapping of other cDNA clones suggested that the variation in mRNA size results from differential utilization of polyadenylylation signals during mRNA processing.Lipoprotein lipase (LPL; triacylglycero-protein acylhydrolase, EC 3.1.1.34) is a lipolytic enzyme involved in the metabolism of triacylglycerol-rich lipoprotein particles (1). It hydrolyzes the triacylglycerol cores of chyromicrons and low density lipoproteins, generating free fatty acids available for extrahepatic tissues. LPL is a glycosylated protein of apparent Mr 55,000 that is synthesized and secreted from parenchymal cells of adipose tissue, heart, skeletal muscle, and mammary gland and is anchored on the luminal surface of the capillary endothelium by membrane-bound heparan sulfate (2, 3). The activity of LPL is markedly enhanced by apolipoprotein C-II present on the surface of triacylglycerol-rich lipoproteins (4). Recent findings (5) indicate that LPL is inhibited by tumor necrosis factor (cachectin). Detailed genetic analyses of several mutant mouse strains suggest that LPL is involved in the cause of atherosclerosis (6). LPL is also present in milk, but the reason for its presence is unknown (1).Since the first description of canine LPL in 1943 (7), a sustained effort has been made to characterize its enzymatic activity and functions (for review, see refs. 1, 2, and 6). However, relatively little is known about the structure of LPL or the gene encoding LPL, or about the factors that govern its expression, despite clinical evidence that familial hypertriglyceridemia is a genetic disorder (8). Recently, Ben-Avram et al. (9) described the NH2-terminal and partial amino acid sequence of bovine LPL and its homology to pancreatic lipase (10). We report here the is...