1INRA, UR 874 UREP, 63100 Clermont-Ferrand, France
2Clermont Université, VetAgro Sup, 63000, Clermont-Ferrand, France
3University of Clermont Ferrand, UMR 6023 LMGE, 63177 Aubière, France
4INRA, UMR 1095 UBP, 63100 Clermont-Ferrand, France
5Montpellier SupAgro, UMR 1208 IATE, 34060 Montpellier, France
*present address: Department of Biological Sciences, Macquarie University, NSW 2109, Australia
**present address: Department of Environmental Sciences, Government College University Faisalabad, 38000-Allama Iqbal Road Faisalabad, Pakistan
Abstract. The respiratory release of CO2 from soils is a major determinant of the global carbon cycle. It is traditionally considered that this respiration is an intracellular metabolism consisting of complex biochemical reactions carried out by numerous enzymes and co-factors. Here we show that the endoenzymes released from dead organisms are stabilised in soils and have access to suitable substrates and co-factors to permit function. These enzymes reconstitute an extracellular oxidative metabolism (EXOMET) that may substantially contribute to soil respiration (16 to 48% of CO2 released from soils in the present study). EXOMET and respiration from living organisms should be considered separately when studying effects of environmental factors on the C cycle because EXOMET shows specific properties such as resistance to high temperature and toxic compounds.