pH-Metric Studies of the Binding of Hydrous Oxide Sols With Pepsin

Abstract

The binding of hydrous oxide sols of aluminium, iron and chromium with pepsin was studied by pH-metric method. The shifts in the titration curves was used as a means to explain the interaction of metals in the hydrous oxide sols with the various ionizable groups of pepsin. The interaction of chromium and aluminium is assumed to take place through the carboxyl groups of pepsin, since the flat segment of the pepsin sol curve lies between pH 3.0 to 6.0 where the carboxyl groups are deprotonated. The similar segment of iron oxide sol-pepsin curve lies in the acid range. Hence, the interaction could not be expected with carboxyl groups, but the phenolic groups of tyrosine may be involved in the binding interaction. The quantitative calculation revealed higher binding in low pH than in higher pH which is in accordance that pepsin contained larger anionic carboxylic groups than basic groups. The order of linking is acidic and basic ranges were identified.