this quantum mechanical study of models for the active sites of pepsins , human renin and retroviral aspartic proteases demonstrates that the replacements of thr-218 from pepsins by ala in human renin and of both ser-35 and thr-218 by alanines in retroviral proteases increases the proton affinity and modulates the charge distribution of those active sites compared to the pepsins .
C0078989
aspartic proteases
C0035094
renin