For instance if you increase the amount of Tris but pH still does not change then will the enzyme activity still proceed normally? If it does change the pH will it change enzyme structure and why?
I realize I'm 4 years late, but wanted to give an answer to this. It appears that tris often has inhibitory effects on amylase activity. Adding more Tris will lead to competitive inhibition with the substrate and will skew the results.
Binding of Tris to Bacillus licheniformis alpha-amylase can affect its starch hydrolysis activity https://www.ncbi.nlm.nih.gov/pubmed/18289113
After 4 years of working in enzymology I've got say tris is really tricky first of all when you use more tris to keep pH at the same as before you will need to re adjust the pH as tris is about 9 but most enzymes work around 6to7.5 (for alpha amylase it's 5.8) if you don't then your enzyme wont work properly ,it needs very low or high pH grade to destroy 3D structure of enzyme ,so we can simply say it will lost it's functionality , if you adjust the pH high concentration can cause some problem such as surrounding substract here amylase and not letting it to connect to enzyme in some cases acid you use to adjust pH has toxic effects on enzyme chlorine in this case but pretty sure the best way is optimization to understand the reaction. Best regards .