Final answer:
Lactase, an enzyme that breaks down lactose, does not directly alter the pH. Instead, in fermentation, it is the byproducts like lactic acid that lower the pH. Enzymes have an optimal pH for activity, and deviation from this can lead to decreased function or denaturation.
Step-by-step explanation:
The enzyme lactase is involved in the breakdown of lactose into glucose and galactose. This process is different from fermentation which typically involves microbial activity leading to the production of organic acids such as lactic acid, resulting in a lower pH or more acidic environment. The role of lactase itself does not directly alter the pH of the environment. Instead, enzymes like lactase have an optimal pH at which they function most efficiently. A deviation from this optimal pH can result in decreased enzyme activity. In the context of fermentation, it is the byproducts of the microbial metabolism, such as lactic acid in lactate fermenters, that can cause a decrease in pH.
The optimum pH for phosphofructokinase, an enzyme in glycolysis, is similarly affected by pH levels. A higher concentration of hydrogen ions (H+), which corresponds to a lower (more acidic) pH, can decrease enzyme activity by affecting the enzyme's structure and consequently its ability to function. This applies to most enzymes, as significant changes in pH can lead to denaturation and a permanent loss in enzymatic activity.
It is essential to distinguish between the effects of enzymes like lactase on substrates, which do not necessarily change pH, and the impact of metabolic products from processes like fermentation, which can lead to increased acidity. The change in the pH of milk during the production of yogurt, for example, is due to the activity of lactic acid bacteria, not the enzyme lactase.