The acid lipase gene family: three enzymes, one highly conserved gene structure. Lohse P,Lohse P,Chahrokh-Zadeh S,Seidel D Journal of lipid research Human gastric lipase (HGL; triacylglycerol lipase; EC 3.1.1.3) plays an important role in the digestion of dietary triglycerides in the gastrointestinal tract, especially in patients suffering from pancreatic lipase deficiencies. The enzyme is secreted by the fundic mucosa of the stomach and hydrolyzes the ester bonds of triglycerides under acidic pH conditions, while cholesteryl esters are not attacked. The 379-amino acid protein is highly homologous to two other acidic lipases, rat lingual lipase (RLL; triacylglycerol lipase; EC 3.1.1.3) and human lysosomal acid lipase (HLAL; cholesteryl esterase; EC 3.1.1.13). To determine whether this remarkable similarity is also present at the genomic level, we have elucidated the respective gene structures by screening three bacteriophage lambda libraries and by polymerase chain reaction-based intron amplification. The genes encoding HGL, RLL, and HLAL are composed of 10 exons interrupted by nine introns and span about 14 kb, 18.7 kb, and 38.8 kb of genomic DNA, respectively. The HGL and RLL gene organizations are identical, suggesting that RLL is the rat gastric lipase expressed in the serous von Ebner glands of the tongue. The positions of the HLAL intervening sequences are also absolutely conserved, except for the location of intron 1. Our results support the concept that HLAL and HGL/RLL are members of a gene family of lipases that most likely have evolved by duplication of an ancestral gene and subsequently assumed distinct roles in neutral lipid metabolism due to sequence divergence and different expression patterns.

[Acid lipase deficiency: Wolman disease and cholesteryl ester storage disease]. Tanaka A Nihon rinsho. Japanese journal of clinical medicine Wolman disease and cholesteryl ester storage disease (CESD) are caused by a deficiency of lysosomal acid lipase activity, resulting in massive accumulation of cholesteryl ester and triglycerides. Wolman disease occurs in infancy, with hepatosplenomegaly, steatorrhea and adrenal calcification. It is fatal before the age of 1 year. In CESD, hepatomegaly may be the only clinical abnormality, although lipid deposition is widespread. Lysosomal acid lipase hydrolyzes both triaclyglycerols and cholesteryl esters, and the enzyme plays an important role in the cellular processing of plasma lipoproteins, and contributes to homeostatic control of lipoprotein levels in blood and prevention of cellular lipid overloading. The gene encoding lysosomal acid lipase was cloned and characterized in 1994, and two mutations of acid lipase gene were found in a patient with Wolman disease, as a compound heterozygote. It is suggested that structural gene defects are also present in CESD cells. However, the reason (s) for the clinical difference between Wolman disease and CESD remain (s) to be studied.

The lipase gene family. Wong Howard,Schotz Michael C Journal of lipid research Development of the lipase gene family spans the change in science that witnessed the birth of contemporary techniques of molecular biology. Amino acid sequencing of enzymes gave way to cDNA cloning and gene organization, augmented by in vitro expression systems and crystallization. This review traces the origins and highlights the functional significance of the lipase gene family, overlaid on the background of this technical revolution. The gene family initially consisted of three mammalian lipases [pancreatic lipase (PL), lipoprotein lipase, and hepatic lipase] based on amino acid sequence similarity and gene organization. Family size increased when several proteins were subsequently added based on amino acid homology, including PL-related proteins 1 and 2, phosphatidylserine phospholipase A1, and endothelial lipase. The physiological function of each of the members is discussed as well as the region responsible for lipase properties such as enzymatic activity, substrate binding, heparin binding, and cofactor interaction. Crystallization of several lipase gene family members established that the family belongs to a superfamily of enzymes, which includes esterases and thioesterases. This superfamily is related by tertiary structure, rather than amino acid sequence, and represents one of the most populous families found in nature. 10.1194/jlr.r200007-jlr200