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The importance of water availability in the reaction equilibrium of hydrolases in forest litters from a M editerranean area: a study on lipases
Author(s) -
Farnet A.M.,
Qasemian L.,
Gil G.,
Ferré E.
Publication year - 2013
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/ejss.12069
Subject(s) - chemistry , soil water , water content , sorption , moisture , litter , hydrolysis , environmental chemistry , total organic carbon , water activity , lipase , ecology , enzyme , organic chemistry , adsorption , biology , geotechnical engineering , engineering
Summary Water is one of the main variables affecting the carbon cycle (carbon storage or assimilation) in soils or litters from the M editerranean area, though in most studies it has been considered via soil moisture measurements only. Here, we investigated the effect of water availability as characterized by water activity, a w , on the equilibrium of enzyme reactions (hydrolysis/synthesis) for litters from three species characteristic of the M editerranean area ( Quercus pubescens L , Q. ilex L . and Pinus halepensis L .). Lipases were used as models and an organic phase was used as the reaction medium to adjust water amount. We found that the activities of hydrolysis/transesterification increased with a w , showing that both can occur at the same a w in litter. Furthermore, these lipase activities in litter decreased for a w close to 1, which has been described with purified lipases in organic media, indicating potential enzyme aggregation. Variations in a w with moisture were studied with sorption isotherms, which were found to be similar (isotherm type 2) for all the studied litters. Water activity is a crucial indicator for soils under hydric stress at small water contents, which should be considered for describing more precisely enzyme functioning and giving valuable information about carbon dynamics in soils or litters.