Enhancing lipase-catalyzed hydrolysis by adding macrocyclic tetraamines

Abstract

Macrocyclic tetraamines (MTs) were employed as novel additives to improve the enzyme's performance in Pseudomonas cepacia lipase (PCL)-catalyzed enantioselective hydrolysis of N-(2-ethyl-6-methylphenyl)alanine methyl ester (NEMPA-ME). Our results showed that the activity of PCL was significantly enhanced and the higher enantioselectivity of the reaction was maintained when some MTs were added to the reaction media. The acceleration of the initial reaction rate greatly depended on MT structure and additive concentration. Among the 21 MTs we tested, 10-(2-hydroxydecyl)-2, 6-dioxo-1,4,7,10-tetraazacyclododecane (MT#20) was found to be the best enzyme activator as 11-fold increase in the initial reaction rate was seen when an optimal concentration of 9.6 mmol/L of the amine was added. Kinetic analysis indicated that the affinity of lipase PCL toward the substrate was modified in the presence of MTs. Molecular modeling suggested that MTs could lead to a more native and stable conformation of lipase, thereby enhancing its enzymatic activity. This is the first systematic study of enhancement of an enzymatic reaction by MT-type additives.