Responsible for synthesis of pseudouridine from uracil-55 in the psi GC loop of transfer RNAs. uridine(55) in tRNA = pseudouridine(55) in tRNA Weakly expressed in maxicells, part of the metY operon that extends to pnp (PubMed:2849753). Belongs to the pseudouridine synthase TruB family. Type 1 subfamily.