What are the 4 regions of digestive system that produce enzymes?

There aren't 4 regions of the digestive system that produce enzymes. The 3 main regions that produce enzymes are the mouth, stomach, and pancreas.

The mouth produces saliva which contains the enzyme amylase that begins the digestion of carbohydrates. The stomach produces gastric juices containing hydrochloric acid and the enzymes pepsin and rennin that start the digestion of proteins. The pancreas produces pancreatic juice that contains the enzymes lipase, amylase, and protease which help break down fats, carbohydrates, and proteins respectively.