The optimum pH for an enzyme such as arginase that acts on arginine in the liver would be:
A) 2.0
B) 7.5
C) 9.7
D) 12.0
The correct answer and explanation is:
The correct answer is C) 9.7.
Arginase is an enzyme found primarily in the liver, where it plays a key role in the urea cycle. It catalyzes the hydrolysis of arginine to ornithine and urea. The optimum pH for an enzyme refers to the pH level at which it exhibits the highest activity, and this value varies based on the enzyme’s environment and function.
Arginase operates most effectively in a slightly alkaline environment. The enzyme’s optimum pH is around 9.7, which is typical for enzymes involved in the urea cycle. This pH range aligns with the physiological conditions in the liver, where arginase is active in breaking down arginine for the production of urea. At this pH, the enzyme’s active site is in its most favorable conformation, allowing the enzyme to interact efficiently with its substrate, arginine.
The pH of the human body varies across different organs and fluids, and enzymes are adapted to their specific environments. For example, enzymes in the stomach, such as pepsin, have an optimum pH around 2.0, which suits the acidic conditions of the stomach. On the other hand, enzymes in the small intestine function optimally at more neutral to slightly alkaline pH levels, closer to 7.5 or 8.0.
Since arginase is involved in the urea cycle in the liver, which has a slightly alkaline pH, the enzyme’s optimal activity at 9.7 reflects the biochemical conditions in that organ. If the pH deviates significantly from this optimum range, the enzyme’s structure and activity could be impaired, reducing its efficiency in processing arginine and generating urea.