Publisher Summary This chapter discusses an engineered lipase that has an altered substrate-binding surface. The engineered enzyme crystallized in a different form than the native enzyme. This necessitated differentiating structural change arising as a consequence of different crystal forms from the changes, arising from the site-specific substitutions that give improved lipase performance. Lipases are a diverse class of enzymes that hydrolyze a range of complex ester-linked triglycerides. Pseudomonas mendocina produces an enzyme that hydrolyzes cutin, a waxy polyester found on the leaf surface. This enzyme is also capable of hydrolyzing ester linkages in a broad variety of compounds including mono- and triglycerides. It should be noted that classic lipases display the phenomenon of micellar activation. This phenomenon manifests itself as an increase in enzymatic activity at substrate concentrations approaching the CMC (critical micellar concentration). The Pseudomonas enzyme does not display any micellar activation. However, by virtue of the ability of the enzyme to hydrolyze triglycerides, it is referred as a lipase and is selected as a parent enzyme to begin engineering efforts to produce an engineered lipase to function as an improved oil-hydrolyzing enzyme for detergent applications.