Synthesis and use of fluorescent molecular probes for measuring cell-surface enzymatic oxidation of amino acids and amines in seawater.

A method for investigating cell-surface enzymatic oxidative deamination of amino acids and amines in seawater was developed. This technique used synthetic fluorescent Lucifer Yellow derivatives of the amino acid lysine and the amine cadaverine as molecular probes to investigate oxidation pathways and rates. The probes were chemically stable under the conditions used and did not adsorb to container surfaces. The oxidative deamination of the fluorescent probes added to phytoplankton cultures and the subsequent production of their fluorescent oxidation products could be selectively detected by HPLC at 250 pM levels. This approach allows selective investigation of cell-surface enzymatic oxidation since neither transport of the probes across the cell membrane nor chemical transformation of the probes occurs. Bacteria were also capable of oxidizing the fluorescent amino acid probe.