Yes, both soaking and sprouting can increase the protein availability in legumes by reducing antinutrients and increasing digestibility.
Legumes contain antinutrients like phytates and tannins, which can bind to minerals and proteins, reducing their absorption. Soaking legumes helps to leach out some of these antinutrients, making the proteins more accessible for digestion. Sprouting takes this a step further. During sprouting, enzymes are activated that break down complex carbohydrates and proteins into simpler, more digestible forms. This process also increases the levels of certain vitamins and minerals, further enhancing the nutritional value of the legumes. The breakdown of proteins into amino acids during sprouting makes them more readily available for the body to use.
Always discard the soaking water of legumes, as it contains the dissolved antinutrients. This prevents you from reintroducing them during cooking.