Catalytic role of Mn(IV) oxide in the formation of humic-enzyme complexes in the soil ecosystem

Abstract
We investigated the effects of short-range ordered Mn(IV), Fe(III), and Al oxides, which are common in soils, on the formation of phenolic-enzyme complexes. Mn(IV) oxide (birnessite) markedly promoted the formation of phenolic-lysozyme complexes with different molecular weights (17–68 kD) in the hydroquinone (diphenol)-lysozyme (enzyme) system. However, promotive effects of Fe(III) and Al oxides on the formation of the complexes were not found under the conditions studied. The results obtained indicate that the catalytic role of Mn(IV) oxides in the formation of humic-enzyme complexes requires close attention in soil ecosystems, because the copolymerization of enzymes during the synthesis of humic susbstances from phenolic compounds produces so-called humic-enzyme complexes.