management of soil enzymes can provide valuable information on microbial
community functions in space and time, related to the understanding key nutrient
cycles, such as nitrogen. However, only small amounts of enzymes can be directly
extracted from soils, so, enzymes are mainly studied through the observation of
their respective activity, which may vary with edapho-climatic conditions [11].
Seasonal variation affects microbial community responses to the environment,
enzymes decrease vertically from the soil surface, vary according to microbial
community distribution and also at landscape level, soil type being a major controlling factor (especially regarding soil texture and SOM content) together with
soil management.
Furthermore, soil type is also a major controlling factor, particularly soil texture
and SOM content. Changes in soil use and soil quality due to management affect
several enzymes long before changes in soil organic matter levels can be detected
[12]. This gives enzyme studies a high potential as a suitable tool for sustainable
ecosystem management in the long-term. Therefore, besides the potential to
anticipate soil quality depletion, enzymatic studies may show the level of degradation of highly disturbed soils and recovery in reclaimed landscapes.
Enzymes can exist on viable cells either internally or on membranes surface, but
they can also be excreted into soil solution and may be found in the soil matrix and
in microbial debris. Except for the case of Error! Reference source not found and a
few other enzymes that exist only in viable cells, most of the other soil enzymes can
be found either in viable or in complexed forms, independent of viable cells, and
stabilized in the soil matrix [11]. Extracellular enzymes or exoenzymes, are secreted
by cells and have the main role of hydrolyzing substrates that are too large or
insoluble to be directly absorbed by microbial cells of some communities. They
maybe secreted by bacteria and fungi as well and, in this case, may be used in
environmental bioremediation, the ones producing hydrolases being especially
useful [13]. When enzymes are found in stabilized forms on colloid surfaces and
incorporated into soils, a degree of degradation of certain contaminants has been
observed in soils. In fact, enzyme activity measurements are used as useful tools to
assess certain heavy metals bioavailability in soils. Moreover, enzymes catalyze
and take part in metabolism processes connected to SOM and to energy processing
in soils. Therefore, the use of indicators for evaluating soil microbial diversity and
microorganism’s activity is key to understanding soil dynamics and fertility.
In summary, soil enzymes are vital not only to maintain soil fertility and health,
but also to protect the environment by degrading pollutant molecules [14].
4 How Enzymes Influence Nitrogen Availability in Soils
The most important soil enzymes belong to three different classes: oxidoreductase,
hydrolase, and lyase. Many of them are directly involved in the processes regulating
the nitrogen cycle. Dehydrogenase (DHA) belongs to the oxidoreductase class that
also includes laccases and all enzymes involved in the oxidation of different
138
C. M. d. S. Cordovil et al.
community functions in space and time, related to the understanding key nutrient
cycles, such as nitrogen. However, only small amounts of enzymes can be directly
extracted from soils, so, enzymes are mainly studied through the observation of
their respective activity, which may vary with edapho-climatic conditions [11].
Seasonal variation affects microbial community responses to the environment,
enzymes decrease vertically from the soil surface, vary according to microbial
community distribution and also at landscape level, soil type being a major controlling factor (especially regarding soil texture and SOM content) together with
soil management.
Furthermore, soil type is also a major controlling factor, particularly soil texture
and SOM content. Changes in soil use and soil quality due to management affect
several enzymes long before changes in soil organic matter levels can be detected
[12]. This gives enzyme studies a high potential as a suitable tool for sustainable
ecosystem management in the long-term. Therefore, besides the potential to
anticipate soil quality depletion, enzymatic studies may show the level of degradation of highly disturbed soils and recovery in reclaimed landscapes.
Enzymes can exist on viable cells either internally or on membranes surface, but
they can also be excreted into soil solution and may be found in the soil matrix and
in microbial debris. Except for the case of Error! Reference source not found and a
few other enzymes that exist only in viable cells, most of the other soil enzymes can
be found either in viable or in complexed forms, independent of viable cells, and
stabilized in the soil matrix [11]. Extracellular enzymes or exoenzymes, are secreted
by cells and have the main role of hydrolyzing substrates that are too large or
insoluble to be directly absorbed by microbial cells of some communities. They
maybe secreted by bacteria and fungi as well and, in this case, may be used in
environmental bioremediation, the ones producing hydrolases being especially
useful [13]. When enzymes are found in stabilized forms on colloid surfaces and
incorporated into soils, a degree of degradation of certain contaminants has been
observed in soils. In fact, enzyme activity measurements are used as useful tools to
assess certain heavy metals bioavailability in soils. Moreover, enzymes catalyze
and take part in metabolism processes connected to SOM and to energy processing
in soils. Therefore, the use of indicators for evaluating soil microbial diversity and
microorganism’s activity is key to understanding soil dynamics and fertility.
In summary, soil enzymes are vital not only to maintain soil fertility and health,
but also to protect the environment by degrading pollutant molecules [14].
4 How Enzymes Influence Nitrogen Availability in Soils
The most important soil enzymes belong to three different classes: oxidoreductase,
hydrolase, and lyase. Many of them are directly involved in the processes regulating
the nitrogen cycle. Dehydrogenase (DHA) belongs to the oxidoreductase class that
also includes laccases and all enzymes involved in the oxidation of different
138
C. M. d. S. Cordovil et al.