Free extracellular enzymes dominate initial peptide hydrolysis in coastal seawater

Shuting Liu, Zhanfei Liu

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Extracellular hydrolysis cleaves large compounds into small molecules to be available to bacteria, which is a key step in decomposition of dissolved organic matter (DOM) in the ocean. To decipher factors controlling initial peptide hydrolysis, tetrapeptide ala-val-phe-ala (AVFA) was incubated for 2 h in coastal seawater treated as unfiltered, 0.2 μm-filtered, mercury chloride (HgCl2)-added, autoclaved, and 0.2 μm-filtered autoclaved. Similar hydrolysis patterns were observed between unfiltered and 0.2 μm-filtered treatments, indicating initial peptide hydrolysis was due to free rather than attached enzymes. Hydrolysis was negligible in autoclaved treatments but significant in the HgCl2 treatment, suggesting that the hydrolytic enzymes were denatured by the high temperature during autoclaving but not affected by HgCl2. Initial AVFA hydrolysis by free enzymes was dominated by aminopeptidases, derived from the hydrolyzed fragments. This study demonstrates the important role of free enzymes in initial peptide hydrolysis in coastal seawater, acting as the immediate responders to labile substrates in the DOM cycling.

Original languageEnglish
Pages (from-to)37-43
Number of pages7
JournalMarine Chemistry
Volume199
DOIs
StatePublished - 20 Feb 2018

Keywords

  • Attached enzymes
  • Coastal seawater
  • Free enzymes
  • Initial hydrolysis
  • Small peptides

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