"PATHWAY: Cofactor biosynthesis; pyrroloquinoline quinone biosynthesis."

"SIMILARITY: Belongs to the PqqB family."

"FUNCTION: May be involved in the transport of PQQ or its precursor to"

"GO:0018189 pyrroloquinoline quinone biosynthetic process"

"show that PqqB is a previously uncharacterized hydroxylase"

"strongly implicate PqqB as a novel non-heme hydroxylase"

"PP_0379 is explicitly annotated as **pqqB** and is genomically adjacent to **pqqC (PP0378)** and **pqqA (PP0380)**"

"PqqB is part of PQQ biosynthesis and is transcriptionally co-induced with neighboring pqq genes under antibiotic stress."

"pqqB upregulated 2.2-fold"

"Insertional disruption of **pqqB (PP_0379)** and **pqqC (PP_0378)** is associated with compromised growth under chloramphenicol"

"PqqB proteins are homologous to the **metallo-β-lactamase fold** superfamily and have an X-ray structure (review cites **PDB 3JXP**)"

"a motif typical of **non-heme metal-binding oxygenases**, supporting an oxygenase-like hypothesis"

"PqqB also appears to contain a **structural Zn²⁺ site** (conserved cysteine motif) that may stabilize the protein rather than directly catalyze the primary chemistry"

"non-heme metallo-oxygenase-like enzyme proposed to hydroxylate PqqA Tyr early in PQQ biosynthesis."

"Direct enzyme assay evidence for KT2440 PqqB substrate specificity and product formation is not present in the retrieved sources"

"the catalytic assignment should be recorded as **inference supported by structure and pathway models**"