Enzyme activity is the reaction rate. The time is not allowed, and the rate is certainly not allowed. If the rate is low because of inaccurate experiments in calculation, the product side will not use this product by referring to your literature in production. Its future will also be affected. If it proves that there is something wrong with your data, you can even say that your paper is false ... the problem is very serious.

Buffer is added because the volume of the solution will change after hydrolysis. The pH of the buffer is more stable than that of a single substance, and the change of enzyme activity is very small and can be ignored.