title: Microbial extracellular enzymes and the marine carbon cycle.
abstract: Extracellular enzymes initiate microbial remineralization of organic matter by hydrolyzing substrates to sizes sufficiently small to be transported across cell membranes. As much of marine primary productivity is processed by heterotrophic microbes, the substrate specificities of extracellular enzymes, the rates at which they function in seawater and sediments, and factors controlling their production, distribution, and active lifetimes, are central to carbon cycling in marine systems. In this review, these topics are considered from biochemical, microbial/molecular biological, and geochemical perspectives. Our understanding of the capabilities and limitations of heterotrophic microbial communities has been greatly advanced in recent years, in part through genetic and genomic approaches. New methods to measure enzyme activities in the field are needed to keep pace with these advances and to pursue intriguing evidence that patterns of enzyme activities in different environments are linked to differences in microbial community composition that may profoundly affect the marine carbon cycle.
authors.affiliation: Department of Marine Sciences, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina 27599-3300, USA. arnosti@email.unc.edu
authors.forename: Carol
authors.initials: C
authors.lastname: Arnosti
mesh_terms: D001419:Bacteria / Q000201:enzymology* / Q000378:metabolism*; D057486:Carbon Cycle; D017753:Ecosystem; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D009792:Oceans and Seas