Phenol Oxidase, perOxidase And Organic Matter Dynamics Of Soil

Soil Biology & Biochemistry 42 (2010) 391e404

Review

Phenol oxidase, peroxidase and organic matter dynamics of soil
Robert L. Sinsabaugh*
Biology Department, University of New Mexico, Albuquerque, NM 87131, USA

Extracellular enzymes mediate the degradation, transformation and mineralization of soil organic matter.
The activity of cellulases, phosphatases and other hydrolases hasreceived extensive study and in many
cases stoichiometric relationships and responses to disturbances are well established. In contrast, phenol
oxidase and peroxidase activities, which are often uncorrelated with hydrolase activities, have been
measured in only a small subset of soil enzyme studies. These enzymes are expressed for a variety of
purposes including ontogeny, defense and theacquisition of carbon and nitrogen. Through excretion or
lysis, these enzymes enter the environment where their aggegrate activity mediates key ecosystem
functions of lignin degradation, humification, carbon mineralization and dissolved organic carbon export.
Phenol oxidases and peroxidases are less stable in the environment than extracellular hydrolases, especially when associated with organicparticles. Activities are also affected, positively and negatively, by
interaction with mineral surfaces. High spatiotemporal variation obscures their relationships with environmental variables and ecological process. Across ecosystems, phenol oxidase and peroxidase activities
generally increase with soil pH, a finding not predicted from the pH optima of purified enzymes. Activities
associated withplant litter and particulate organic matter often correlate with decomposition rates and
potential activities generally increase with the lignin and secondary compound content of the material. At
the ecosystem scale, nitrogen amendment alters the expression of phenol oxidase and peroxidase
enzymes more broadly than culture studies imply and these responses correlate with positive and negativechanges in litter decomposition rates and soil organic matter content. At the global scale, N amendment of
basidiomycete-dominated soils of temperate and boreal forest ecoystems often leads to losses of oxidative
enzyme activity, while activities in grassland soils dominated by glomeromycota and ascomycetes show
little net response. Land use that leads to loss of soil organic matter tends toincrease oxidative activities.
Across ecosystems, soil organic matter content is not correlated with mean potential phenol oxidase and
peroxidase activities. A multiple regression model that includes soil pH, mean annual temperature, mean
annual precipitation and potential phenol oxidase activity accounts for 37% of the variation in soil organic
matter (SOM) content across ecosystems (n ¼ 63); asimilar model for peroxidase activity describes 32% of
SOM variance (n ¼ 43). Analysis of residual variation suggest that suites of interacting factors create both
positive and negative feedbacks on soil organic matter storage. Soils with high oxygen availability, pH and
mineral activity tend to be substrate limited: high in situ oxidative activities limit soil organic matter
accumulation.Soils with opposing characteristics are activity limited: low in situ oxidative activities
promote soil organic matter storage.
Ó 2009 Elsevier Ltd. All rights reserved.

Keywords:
Phenol oxidase
Peroxidase
Soil organic matter
Litter decomposition
Extracellular enzyme activity

1. Introduction
Extracellular enzymes mediate the degradation, transformation
and mineralization of soilorganic matter. The activity of cellulases,
phosphatases and other hydrolases has received extensive study
and in many cases stoichiometric relationships and responses to
disturbances are well established (Sinsabaugh et al., 2008). In

* Corresponding author. Tel.: þ1 505 277 9043.
E-mail address: rlsinsab@unm.edu
0038-0717/$ e see front matter Ó 2009 Elsevier Ltd. All rights reserved....