In a small bowl, mix together the yeast and warm water.

Let it stand for 5 minutes.

Stir in the warm buttermilk.

Set aside. In a large bowl, mix together the flour, sugar, salt, baking powder, and baking soda.

Cut in the shortening until the mixture resembles coarse cornmeal.

Stir in the yeast mixture.

Turn the dough out onto a lightly floured surface and knead gently for about 30 seconds.

Roll out the dough to ½-inch thickness and cut with a biscuit cutter.

Place the biscuits on a lightly greased baking sheet with their sides not quite touching, cover, and let rise until double, about 30 to 45 minutes.

Bake in a preheated 450° oven 8 to 10 minutes or until done.

Remove from the oven and immediately brush the tops with melted butter.