AUTHOR=Gebauer Jan , Pietruszka Jörg , Classen Thomas 

TITLE=Expression and characterization of PrnC—a flavin-dependent halogenase from the pyrrolnitrin biosynthetic pathway of Pseudomonas protegens Pf-5

JOURNAL=Frontiers in Catalysis

VOLUME=3

YEAR=2023

URL=https://www.frontiersin.org/journals/catalysis/articles/10.3389/fctls.2023.1231765

DOI=10.3389/fctls.2023.1231765

ISSN=2673-7841

ABSTRACT=<p><bold>Introduction:</bold> The antimicrobial pyrrolnitrin from <italic>Pseudomonas</italic> strains is formed in four steps from tryptophan and comprises two flavin-dependent halogenases. Both PrnC and PrnA can carry out regioselective chlorination and bromination and are carrier protein-independent. Whilst the tryptophan halogenase PrnA has been studied in detail in the past, this study focuses on the pyrrole halogenating enzyme PrnC.</p><p><bold>Methods:</bold> The halogenating enzyme PrnC, as well as the essential electron suppliers, the flavin reductases, have been produced soluble in <italic>E. coli</italic>. Furthermore, a screening of a rational compound library revealed that the pyrrole is essential for substrate recognition; however, the substitution pattern of the benzene ring is not limiting the catalysis.</p><p><bold>Results and discussion:</bold> This renders PrnC to be a synthetically valuable enzyme for the synthesis of pyrrolnitrin congeners. For its natural substrate monodechloroaminopyrrolnitrin (MDA), the K<sub>M</sub> value was determined as 14.4 ± 1.2 µM and a k<sub>cat</sub> of 1.66 ± 0.02 min<sup>−1</sup>, which is comparable to other halogenases.</p>