Mechanistic and structural insights into the bifunctional enzyme PaaY from Acinetobacter baumannii

• Published in: Structure (London) Vol. 31; no. 8; pp. 935 - 947.e4
• Main Authors: Jiao, Min, He, Wenbo, Ouyang, Zhenlin, Qin, Qian, Guo, Yucheng, Zhang, Jiaxin, Bai, Yixin, Guo, Xiaolong, Yu, Qinyue, She, Junjun, Hwang, Peter M., Zheng, Fang, Wen, Yurong
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 03.08.2023
• Subjects: Acinetobacter baumannii; Acinetobacter baumannii - genetics; Anti-Bacterial Agents - chemistry; bifunctional enzyme; Biofilms; Carbonic Anhydrases - genetics; PaaY; phenylacetic acid pathway; structure and function; Acinetobacter baumannii; bifunctional enzyme; PaaY; phenylacetic acid pathway; structure and function
• DOI: 10.1016/j.str.2023.05.015
• ISSN: 0969-2126

PaaY is a thioesterase that enables toxic metabolites to be degraded through the bacterial phenylacetic acid (PA) pathway. The Acinetobacter baumannii gene FQU82_01591 encodes PaaY, which we demonstrate to possess γ-carbonic anhydrase activity in addition to thioesterase activity. The crystal structure of AbPaaY in complex with bicarbonate reveals a homotrimer with a canonical γ-carbonic anhydrase active site. Thioesterase activity assays demonstrate a preference for lauroyl-CoA as a substrate. The AbPaaY trimer structure shows a unique domain-swapped C-termini, which increases the stability of the enzyme in vitro and decreases its susceptibility to proteolysis in vivo. The domain-swapped C-termini impact thioesterase substrate specificity and enzyme efficacy without affecting carbonic anhydrase activity. AbPaaY knockout reduced the growth of Acinetobacter in media containing PA, decreased biofilm formation, and impaired hydrogen peroxide resistance. Collectively, AbPaaY is a bifunctional enzyme that plays a key role in the metabolism, growth, and stress response mechanisms of A. baumannii. [Display omitted] •AbPaaY is a bifunctional enzyme with γ-carbonic anhydrase and thioesterase activities•AbPaaY contains a canonical γ-carbonic anhydrase active site and forms a homotrimer•The AbPaaY trimer contains domain-swapped C-termini•AbPaaY plays a key role in metabolism, biofilm formation, and stress response Jiao et al. provide mechanistic and structural insights into the Acinetobacter baumannii PAA catabolic pathway enzyme PaaY and its involvement in environmental stress response. AbPaaY assembles as a domain-swapped homotrimer, contains a γ-carbonic anhydrase active site and functions both as a γ-carbonic anhydrase and as a thioesterase.