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Temperature sensitivities of extracellular enzyme V max and K m across thermal environments
- Source :
- Global Change Biology. 24:2884-2897
- Publication Year :
- 2018
- Publisher :
- Wiley, 2018.
-
Abstract
- The magnitude and direction of carbon cycle feedbacks under climate warming remain uncertain due to insufficient knowledge about the temperature sensitivities of soil microbial processes. Enzymatic rates could increase at higher temperatures, but this response could change over time if soil microbes adapt to warming. We used the Arrhenius relationship, biochemical transition state theory, and thermal physiology theory to predict the responses of extracellular enzyme Vmax and Km to temperature. Based on these concepts, we hypothesized that Vmax and Km would correlate positively with each other and show positive temperature sensitivities. For enzymes from warmer environments, we expected to find lower Vmax , Km , and Km temperature sensitivity but higher Vmax temperature sensitivity. We tested these hypotheses with isolates of the filamentous fungus Neurospora discreta collected from around the globe and with decomposing leaf litter from a warming experiment in Alaskan boreal forest. For Neurospora extracellular enzymes, Vmax Q10 ranged from 1.48 to 2.25, and Km Q10 ranged from 0.71 to 2.80. In agreement with theory, Vmax and Km were positively correlated for some enzymes, and Vmax declined under experimental warming in Alaskan litter. However, the temperature sensitivities of Vmax and Km did not vary as expected with warming. We also found no relationship between temperature sensitivity of Vmax or Km and mean annual temperature of the isolation site for Neurospora strains. Declining Vmax in the Alaskan warming treatment implies a short-term negative feedback to climate change, but the Neurospora results suggest that climate-driven changes in plant inputs and soil properties are important controls on enzyme kinetics in the long term. Our empirical data on enzyme Vmax , Km , and temperature sensitivities should be useful for parameterizing existing biogeochemical models, but they reveal a need to develop new theory on thermal adaptation mechanisms.
- Subjects :
- Global and Planetary Change
Biogeochemical cycle
010504 meteorology & atmospheric sciences
Ecology
biology
Chemistry
Global warming
Q10
Climate change
04 agricultural and veterinary sciences
Plant litter
biology.organism_classification
Atmospheric sciences
01 natural sciences
Neurospora
Carbon cycle
040103 agronomy & agriculture
Litter
0401 agriculture, forestry, and fisheries
Environmental Chemistry
0105 earth and related environmental sciences
General Environmental Science
Subjects
Details
- ISSN :
- 13652486 and 13541013
- Volume :
- 24
- Database :
- OpenAIRE
- Journal :
- Global Change Biology
- Accession number :
- edsair.doi...........4c5a86cc14626fc126db54377843463e