a, Strategy for selection of alternative catalysts for cross-coupling reactions using SSNs. b, Bacterial fusion enzymes (P450-RhFRed) catalyze cross-coupling reactions with naphthols, demonstrating complementary reactivity to KtnC. The top hits from an initial screen of 23 enzymes were purified for further quantification of reaction yield and selectivity. Reaction conditions: 10 μM purified P450-RhFRed in the presence of 5 mM glucose-6-phosphate, 1 mM NADP+, 1 U/mL glucose-6-phosphate dehydrogenase, and substrates in a 1:1 molar ratio in lysate reactions (1 mM 39 and 1 mM 31 or 40) or 1:3 molar ratio in reactions with purified enzyme (100 μM 39 and 300 μM 31 or 40) in tricine buffer pH 8.3 at 30 ˚C for 16 h; cross-coupling reactions reported as percent yields to major product with cross-coupling site-selectivity in parentheses.