Bypassing evolutionary dead ends and switching the rate-limiting step of a human immunotherapeutic enzyme.

ABSTRACT: The Trp metabolite kynurenine (KYN) accumulates in numerous solid tumours and mediates potent immunosuppression. Bacterial kynureninases (KYNases), which preferentially degrade kynurenine, can relieve immunosuppression in multiple cancer models, but immunogenicity concerns preclude their clinical use, while the human enzyme (HsKYNase) has very low activity for kynurenine and shows no therapeutic effect. Using fitness selections, we evolved a HsKYNase variant with 27-fold higher activity, beyond which exploration of >30 evolutionary trajectories involving the interrogation of >10⁹ variants led to no further improvements. Introduction of two amino acid substitutions conserved in bacterial KYNases reduced enzyme fitness but potentiated rapid evolution of variants with ~500-fold imp

SUBMITTER: Blazeck J 

PROVIDER: S-EPMC9717613 | biostudies-literature | 2022 Oct

REPOSITORIES: biostudies-literature