What enzyme begins the digestion of proteins?

I will assume that your question refers to humans. As it is specifically about enzymatic degradation of proteins, the short answer is pepsin, the protease contained in gastric juice. read more

Saliva contains the digestive enzyme, which works on carbohydrate starches, like breads, potatoes, or pasta, to help break them down into simple sugars. Some digestion of fat also starts in the mouth when a small amount of lingual lipase is secreted and mixes with saliva. read more

Amino acids can be used by your body to form important cellular structures, such as enzymes, antibodies, hormones, muscle proteins, and collagen. Protein digestion begins with the action of an enzyme called pepsin. Pepsin is the active protein-digesting enzyme of the stomach. read more