Apoint mutation in the mrna for an enzyme results in the replacement of leucine with alanine in the resulting enzyme molecule. why does this change in amino acids have little effect on the biological activity of the enzyme?

The is because both are hydrophobic (due to their neutral side chains) and have approximately the same net charge. The isoelectric point of leucine at 25 degrees centigrade is 6.04 while that of alanine is 6.11.  Therefore, this mutation does not change the structure of the protein hence does not affect its function (if not considerably).

where is the scientific experiment?