The effect of chemical structure on hydrolysis pathways of small peptides in coastal seawater

The hydrolysis pathway of a given peptide or protein in seawater, how it is hydrolyzed by extracellular enzymes, may depend on its chemical structure specific amino acid composition. This knowledge important for better understanding the first steps decomposition labile organic matter that often dominated proteins. can be estimated from fragments small peptides through incubation experiments. Here we incubated group with different compositions coastal including tetrapeptides alanine-valine-phenylalanine-alanine (AVFA) and modifications N terminal A valine (V), serine (S), arginine (R) aspartic (D) (i.e., VVFA, SVFA, RVFA, DVFA). Through these incubations, evaluated effect composition pathways roles types peptidases. Our results showed aminopeptidases preferentially R (29–100% total peptidases), followed V (30–90%) S (20–51%), but were ineffective acidic D (0–14%). pattern indicates N-terminal affects environment. For acids uncharged side chains, preferred hydrophobic A, to polar S, those charged they positively-charged negatively-charged D. also suggest if could not access peptide, carboxypeptidases and/or endopeptidases will hydrolyze it, leading similar rates among although their differ. further demonstrated comparing trialanine (AAA), AVF, AVFA, VFA, phenylalanine-alanine-serine-tryptophan-glycine-alanine (FASWGA) SWGA. Overall, this study show shed new lights early nitrogen degradation cycling marine environments.