{'fraction_non_alphanumeric': 0.02457627118644068, 'fraction_numerical': 0.011864406779661017, 'mean_word_length': 5.524861878453039, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Ferulic acid decarboxylase (Fdc1) controls oxidative maturation of the prFMN cofactor.

Prenylated FMN (prFMN) is a recently discovered modified flavin cofactor containing an additional non-aromatic ring, connected to the N5 and C6 atoms. This cofactor underpins reversible decarboxylation catalysed by the widespread UbiD-enzyme family, and is produced by the flavin prenyltransferase UbiX. Oxidative maturation of the UbiX product prFMNH2 to the corresponding oxidized prFMNiminium is required for Fdc1 (a UbiD-type enzyme) activity. However, it is unclear what role the Fdc1-enzyme plays in this process. Here we demonstrate that in the absence of Fdc1, prFMNH2 oxidation by O2 proceeds via a transient semiquinone prFMNradical species and culminates in a remarkably stable prFMN-hydroperoxide species. Neither forms of prFMN are able to support Fdc1 activity. Instead, enzyme activation using O2-mediated oxidation requires prFMNH2 binding prior to oxygen exposure, confirming that UbiD-enzymes play a role in O2 mediated oxidative maturation. In marked contrast, alternative oxidants such as potassium ferricyanide support prFMNiminium formation both in solution and in Fdc1.