A highly enantioselective aminopeptidase from sunflower seed—Kinetic studies, substrate mapping and application to biocatalytic transformations

Abstract The sunflower seed ( Helianthus annuus L.) major aminopeptidase primary specificity has been assessed with a number of specially designed amino acid amides and alkyl esters. Studies with amino acid 4-nitroanilides with straight alkyl side chains suggest the enzyme possesses an S 1 hydrophobic binding site of limited size and effects of substrate sorption are present in both its binding and turnover. The enzyme S 1 ′-subsite is able to accommodate a number of different leaving groups—primary amide, one- and two-ring condensed aromatic structures, amino acid residues and alkyl ester moieties. The hydrolysis of amide substrates is affected by both their P 1 and the P 1 ′ part. The replacement of the amide leaving group with an ester one tents to minimize the P 1 -part effect. The enzyme's high enantioselectivity towards the configuration of the substrate P 1 -part has been successfully utilized for resolution of racemic amino acid amides.