Deforestation alters protease regulation by amino acids

Abstract

Protease activity is regulated by numerous complex mechanisms in soil. In this study, we investigated the regulatory effect of the end product of the proteolytic reaction, amino acids, on protease activity in two forest soils and their deforested counterparts, which are located in two mountainous regions (Delvara and Minoodasht) of Iran. The protease activity was measured during the incubation of the soils treated with l-arginine and l-histidine. Our result indicated that, in general, amending the soils with the amino acids caused significant increases in the protease activity after a lag time of 2–5 days. However, the stimulatory effects of the amino acids on the protease activity were clearly affected by the land use so that the activity ratios of the amino acid-amended to the non-amended soils were between 3.1 and 3.5 in forest and 4.7–4.9 in the deforested counterparts of Delvara soil. Similarly, in the Minoodasht region, the ratio ranged 1.6–2.0 for the forest and 4.4–6.5 for the deforested counterpart. In addition, deforestation in the Minoodasht region significantly decreased indices of protease production and persistence. In l-arginine-amended soils, deforestation decreased protease production by 25 % while the protease persistence was decreased by 88 %. In l-histidine-amended soils, protease production was decreased by 70 % and protease persistence was decreased by 59 %, due to deforestation. Overall, we conclude that amending the soils with the amino acids increased the activity of protease and that the rate of increase is clearly affected by the management history.