Catalyzes the conversion of dethiobiotin (DTB) to biotin by the insertion of a sulfur atom into dethiobiotin via a radical- based mechanism (By similarity). MNSISASAIVLWKNTPLPFVVKSYPMSTLTTDWQHLANLALADECLSRDQARAVLQAPDTELLNQLAAAYRVRYHYWGNRVRLHYLLNAQSGLCPEDCHYCSQSKISTAEIEKYPLLSQEKILAAADRAAHLKAGTFCMVISGRSPSEKVFEQVLAAIRAVKERYPLKICACLGLLTPEQTARLAAAGVDRVNHNLNTSENFYSEICTTHTFRDRDQTLANIQAAGITTCSGGILGMGESDDDVIDLALFLRQRQVTSVPVNFLIPIPGTPLGEQHTLNPRHCLRILVLFRFLLPRQEIRIAGGREVHLRSLQPLGLYAANSMFIGDYLTTPGQAPHQDWQMIADAGFVLEDPEGRAIAP bioB BIOB_THEEB Biotin synthase tll0661 360