What is the Difference Between Pepsin and Renin?

Pepsin and renin are both proteases, but they have different functions and are found in different parts of the body. Here are the main differences between them:

1. Origin and Secretion: Pepsin is secreted by the gastric glands of the stomach in an inactive form, which is then converted into its active form by hydrochloric acid (HCl). Renin, on the other hand, is secreted by the juxtaglomerular cells of the kidneys in an active form.
2. Function: Pepsin is the principal digestive protease in the stomach, helping to break down proteins into peptides and amino acids. Renin is involved in the renin-angiotensin system, which helps to control blood pressure by resulting in an increase in the rate of reabsorption of Na+ ions in the nephrons.
3. pH Stability: Pepsin is irreversibly denatured when exposed to neutral pH conditions, while renin is fully stable and optimally active in the same conditions. This difference in pH stability is due to structural differences in the turn and joint regions of the β-barrel and ψ-loops, as well as amino acid composition.
4. Amino Acid Composition: Pepsin has an abundance of polar and aspartic acid residues, which is a common trait with other acid-stable enzymes. Renin, however, has increased levels of basic amino acids. The solvent-exposed basic residues in renin allow for extensive salt bridge formation, while in pepsin, these residues are protonated and serve to form stabilizing hydrogen bonds at low pH.

Comparative Table: Pepsin vs Renin

Here is a table comparing the differences between pepsin and renin:

Pepsin is a protease produced by the stomach, which helps in the digestion of proteins by breaking them down into peptides and amino acids. On the other hand, renin is an aspartic protease enzyme produced by the juxtaglomerular cells of the kidneys, which also acts as a hormone to control blood pressure.