Left: Acyl binding site of CAL-A mutant G237Y modeled with docked p-nitrophenyl caproate to illustrate the position of this medium chain fatty acid in the CAL-A binding tunnel (shown as wireframe). The tyrosine substitution in helix aD2 is shown as red stick, the active site residues are shown in green. Right: Structure of CAL-A indicating positions T221 and I301, which had the most pronounced effect on the trans-fatty acid selectivity of this lipase.