Lipases have been demonstrated to be excellent biocatalysts for synthesis and decomposition of various esters, transesterification, and optical resolution of racemic mixtures. In fact, lipases have been used for production of digestants and/or flavorings, production of clinical laboratory reagents, detergent enzymes and/or fats, as well as production of optically active intermediates for agricultural chemicals and pharmaceutical preparations.
Among lipases, animal pancreatic lipases are well known, but it is primarily microbial lipases that are often used industrially. For most of these lipases, their genes have been cloned and the amino acid sequences thereof are also known (Candida rugosa: Non-patent Document 1; Rhizopus delemar: Non-patent Document 2; Bacillus subtilis: Non-patent Document 3; Staphylococcus aureus: Non-patent Document 4; and Pseudomonas aeruginosa: Non-patent Document 5).
Lipases produced by filamentous fungi or bacteria such as Bacillus spp., Staphylococcus spp. or Pseudomonas spp. are used for industrial purposes. These lipases principally target a higher fatty acid (containing 16 or more carbon atoms) as a substrate, while those targeting a short-chain fatty acid (containing 6 or less carbon atoms) as a substrate are called esterases. No lipase is known which successfully recognizes a medium-chain fatty acid and shows not only hydrolytic activity, but also esterification activity.
Triglycerides having medium-chain fatty acids are hydrolyzed by the action of not only pancreatic lipases, but also gastric lipases, indicating that lipases are also advantageous in digestion and/or absorption of triglycerides (Non-patent Document 6). Moreover, the absorbed medium-chain fatty acids are less likely to be resynthesized into triglycerides in intestinal tract cells of the small intestine. They are transported through the portal vein to the liver and burned as energy. In contrast, higher fatty acids are resynthesized in intestinal tract cells, absorbed through the lymph and transported to the liver, and in some cases may be accumulated as fat. This means that higher fatty acids are accumulative in the body, whereas medium-chain fatty acids are not accumulative. For this reason, healthy fats and oils are produced by transesterification between medium-chain fatty acid triglycerides and common edible fats and oils.
Non-patent Document 1: Kawaguchi et al., Nature, 341, 164-166 (1989)
Non-patent Document 2: Haas et al., Gene, 109, 107-113 (1991)
Non-patent Document 3: Dartois et al., B. B. A., 1131, 253-260 (1992)
Non-patent Document 4: Lee et al., J. Bacteriol., 164, 288-293 (1985)
Non-patent Document 5: Wohlfarth et al., J. General Microbiology, 138, 1325-1335, (1992)
Non-patent Document 6: I. Ikeda, Y. Tomari, M. Sugano, S. Watanabe, and J. Nagata: Lipids, 26, 369-373 (1991)