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Formation and Activity of Urease‐Tannate Complexes Affected by Aluminum, Iron, and Manganese
Author(s) -
Gianfreda Liliana,
Rao Maria A.,
Violante Antonio
Publication year - 1995
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1995.03615995005900030024x
Subject(s) - tannic acid , chemistry , urease , adsorption , polymerization , nuclear chemistry , enzyme , molecule , manganese , inorganic chemistry , polymer , polymer chemistry , organic chemistry
The formation of active enzymatic complexes, obtained by the interaction of urease, tannic acid, and soluble and insoluble species of Al, Fe, or Mn, was studied. Tannic acid strongly inhibited urease activity (inhibition constant, K i = 0.040 m M ). The dependence of kinetic parameters ( V max and K m ) on tannic acid concentration suggests a pure uncompetitive inhibition mechanism. Soluble and insoluble urease‐tannate complexes were formed by increasing both the contact time and the tannic acid/urease ratios. Soluble (FeCl 3 , MnCl 2 , and OH‐Al polymers) and insoluble (Fe 2 O 3 and MnO 2 ) inorganic components differently influenced the interaction of urease with tannic acid molecules and the residual activity of the immobilized enzyme. An increased removal of urease molecules from solution as well as an enhanced residual enzymatic activity of urease complexes was observed in the presence of all the additives. Soluble species (FeCl 3 and OH‐Al polymers) probably acted as flocculating agents or promoted the formation of more active enzymatic complexes. On the contrary, MnO 2 showed a predominant polymerizing action on tannate molecules that gave rise to insoluble aggregates occluding urease molecules. Adsorption, as opposed to polymerization, probably occurred in the presence of Fe 2 O 3 .