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Steapsin belongs to the class of digestive enzymes called lipases found in the pancreatic juice that catalyzes the hydrolysis of triglycerides (main constituent in vegetable oils and animal fat) to fatty acids and glycerol. When food travels through the oral cavity and down the esophagus into the stomach, enzymes such as pepsin are released where it cleaves large proteins into smaller peptide fragments so further digestion and absorption can occur in the duodenum, the tube that connects the stomach to the small intestine. Fats are minimally digested in the stomach by gastric lipases but most digestion occurs in the small intestine.

I. Function The lipase steapsin is secreted from the pancrease to break down triglycerides to liberate the fatty acids and glycerol. The free fatty acids can then be absorbed to the liver and kidneys where it may be converted to glyceraldehyde 3-phosphate, a constituent in the process of glycolysis to ultimately generate energy in the form of ATP via the citric acid cycle. • Or, break down triglycerides to form free fatty acids to cross intestinal barrier to be repackaged into adipose tissue

II. Characterization Method in quantifying steapsin activity in vitro: - Used olive oil as the ‘fat’ to be broken down - Steapsin was added, and experiments were conducted, turned olive oil into glycerol and free fatty acids - Added phenolphthalein and titrated against NaOH - Amount of NaOH added correlated to steapsin activity

A. pH • Basic conditions – 10% steapsin degradation per hour • Neutral conditions – 10% steapsin degradation per hour • Acidic conditions – 0.02M of HCl decreased steapsin activity by 80%

B. Temperature • 37 C – 8% degradation per hour • 40 C – 10% degradation per hour • 50 C – 99% degradation per hour • 60 C – 99% degradation in 10 minutes

C. Trypsin (Steapsin inhibitor) • Produced in pancreas and secreted as trypsinogen (inactive precursor of trypsin) • Trypsin activated by enteropeptidase (secreted from duodenum) to prevent autodigestion of the pancreas. • Trypsin inactivates steapsin

D. Egg Albumen (Trypsin inhibitor) • When trypsin, steapsin and egg albumen present in solution, trypsin is neutralized • Steapsin activity unchanged

E. Bile • Bile does not hydrolyse fats independently, acts as emulsifier, providing greater surface area • Combined with steapsin, activity increased by nearly two fold

Conclusions When eating greasy foods: 1. Eat protein (e.g. egg whites, lean meat) to allow steapsin to remain active for a longer period to break down triglycerides. 2. Remember to expend the energy from these fatty acids to prevent it from being incorporated into adipose tissue.