Recently, lipases have been purified from mammalian, bacterial, fungal and plant sources by different methodologies. Purified lipases subsequently have been characterized for molecular size, metal binding capabilities, glycoside and phosphorus contents, and substrate specificities. Primary structures of several lipases have been determined either from amino acid or nucleic acid sequences. Lipases sequenced to date share sequence homologies including a significant region, Gly-X-Ser-X-Gly, that is conserved in all. The Ser residue is suspected to be essential for binding to lipid substrates.

The purified multienzyme complex of fatty acid oxidation from Escherichia coli was found to possess 3-hydroxyacyl-coenzyme A (CoA) epimerase and cis-A3-trans-A2-enoyl-CoA isomerase activities in addition to the previously identified enoyl-CoA hydratase, L-3-hydroxyacyl-CoA dehydrogenase, and 3-ketoactyl-CoA thiolase activities. Evidence is presented in support of the proposed association of all five enzyme activities with one protein which apparently is composed of two types of subunits and which can exist in several aggregated forms. The five component enzymes of the complex were rapidly inactivated by tris(hydroxymethyl)aminomethane, whereas they remained active in the presence of potassium phosphate.

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