Mom's yeast biscuits

My mom made these to be smothered in sausage gravy or butter with jam. Unbelievably good.

1 package dry yeast (about 2 1/4 teaspoons)
1/2 cup warm water (105° to 115°)
5 cups all-purpose flour
1/4 cup sugar
1 teaspoon baking powder
1 teaspoon baking soda
1 teaspoon salt
1/2 cup vegetable shortening
2 cups low-fat buttermilk
Cooking spray
1 tablespoon melted butter

Dissolve yeast in warm water in a small bowl; let stand 5 minutes.

Combine the dry ingredients (flour through salt) in a large bowl. Cut in shortening with a pastry blender until mixture resembles coarse meal. Add yeast mixture and buttermilk; stir just until moist. Cover and chill 1 hour.

Turn dough out onto a heavily floured surface; knead lightly 5 times. Roll dough to a 1/2-inch thickness; cut with a 3-inch juice glass. Place on a baking sheet coated with cooking spray. Brush melted margarine over biscuit tops. Bake in preheated oven at 450° for 12 minutes or until golden.