Place catfish in single layer in 13x9-inch dish. In small bowl, mix buttermilk and pepper sauce with whisk; pour over fish. Cover; refrigerate 8 hours, turning once.
Remove fish from refrigerator; let stand at room temperature 10 minutes. Meanwhile, in shallow dish, mix cornmeal, both flours, salt, black pepper, red pepper and garlic powder. Remove fish from buttermilk mixture, allowing excess to drip off. Coat fish with cornmeal mixture, shaking off excess.
In deep fryer or heavy saucepan, heat 2 inches oil to 360°F. Line 15x10-inch pan with paper towel; place cooling rack in pan. Fry fish in batches 2 minutes on each side or until golden brown. Place on rack in pan. Keep warm in 225°F oven until serving time. Serve with lemon wedges.