Simulation Study of Soluble Toxic Oligomeric Structures of Amyloid-Beta

Abstract

Ammonia lyases and aminomutases are emerging as important enzymatic systems, not only in green synthetic routes to chiral amines, but also as potential target for enzyme therapeutic for treating diseases such as phenylketonuria and cancer (1). On the other hand, b-amino acids harbor many applications in their free form and as building blocks of bioactive compounds (2, 3). Although, these eco-friendly biocatalytic routes have been extensively explored, they are far from optimal. The aim of this work is to engineer a phenylalanine aminomutase (PAM) to acquire lyase properties for the efficient production of enantio-pure b-Phe (key component of taxol ( 2)). Thus, this study was guided by molecular modeling techniques to decipher which structural components functionally separate PAM and the phenylalanine ammonia lyase (PAL). Despite the great structural similarity of the active site of these enzymes, PAL is a-selective with much faster deamination rates relative to PAM, which exhibits 50% aand bregioselectivity (1, 4). Recent studies have implicated loop regions as key structural determinants between PAM and PAL (5). Here, we report novel insight into the implications of the active-site loop residues of PAM, which influence mutase/lyase activity. Several mutants were proposed, cloned, expressed and characterized. Overall, this enzyme engineering work represents the first successful attempt to convert a PAM to a PAL through strict mutase-to-lyase residue mutations. Such a breakthrough may guide future investigations into the functional determinants of these enzymes and possibly foster the engineering of faster PAM variants used for the efficient synthesis of b-Phe.