HYDROLYSIS OF PEPTIDES IN SEAWATER AND SEDIMENT

Protein hydrolysis and subsequent peptide production appear to be the links between degradation of protein and production of free amino acid s in the marine environment. This model has not yet been fully demonst rated because neither presence of peptides nor peptide hydrolysis has been directly measured in seawater or sediments. Fluorescent Lucifer Y ellow (LYA)-derivatives of several peptides were synthesized and teste d for use as models in an investigation of peptide hydrolysis in seawa ter and sediment. We demonstrated that these LYA-derivatives behave to some degree as the natural peptides by showing that LYA-dialanine eff ectively competes with dialanine (ala(2)) for the active sites of micr obial hydrolytic enzymes found in seawater. LYA-derivatives of ala(2), ala-leu and ala(4) hydrolyzed to smaller peptides or free amino acids in both seawater and sediments. In seawater, hydrolysis of the longer peptide, LYA-ala(4) was 90 X faster than hydrolysis of LYA-ala(2) and 30 X faster than LYA-ala-leu. In sediments, rapid disappearance of th e initially-added substrate LYA-ala(4) from pore waters was followed b y slower production of LYA-ala(3), LYA-ala(2) and LYA-ala. Hydrolysis was not random; preferential cleavage of certain peptide bonds occurre d.