Which of the following is not a digestive enzyme in the human system?

The correct answer is B. Gastrin. Gastrin is a hormone that stimulates the secretion of gastric acid and pepsin. It is not a digestive enzyme itself.

Trypsin is a digestive enzyme that breaks down proteins into smaller peptides. It is produced in the pancreas and secreted into the small intestine.

Ptyalin is a digestive enzyme that breaks down starch into maltose. It is produced in the salivary glands and secreted into the mouth.

Pepsin is a digestive enzyme that breaks down proteins into smaller peptides. It is produced in the stomach and secreted into the stomach.