TABLE 2.

Enzyme activities of three P. piscicida isolates against six synthetic fluorogenic substrates 48 h postinoculation onto plates containing V. vulnificus^a

Fluorogenic substrateb	Substrate detects:	Enzyme activity from colony or zone of inhibition	Enzyme activity (15 min/1 h) from:
			Pseudoalteromonas piscicida strains			Lawns of Vibrio vulnificus
			DE1-A	DE2-A	DE2-B
AFC-002 (l-Arg-AFC)	Aminopeptidase B	Colony	−/+	−/+	−/+	−/−
		Zone	−/−	−/+	−/−
AFC-008 (l-Lys-AFC)	Aminopeptidase B	Colony	−/−	−/+	−/+	+/+
		Zone	−/−	−/−	−/−
AFC-059 (d-Pro-Phe-Arg-AFC)	Serine protease (trypsin-like)	Colony	+/+	+/+	−/+	+/+
		Zone	−/−	+/+	+/+
AFC-094 (methoxysuccinyl-Ala-Ala-Pro-Val-AFC)	Serine protease (neutrophil elastase)	Colony	−/−	−/−	−/−	−/−
		Zone	−/−	−/−	−/−
AFC-096 (methoxysuccinyl-Ala-Ala-Pro-Met-AFC)	Serine protease (chymotrypsin-like, cathepsin G-like)	Colony	+/+	+/+	−/+	−/−
		Zone	−/−	−/+	−/+
AFC-120 (N-acetyl-Tyr-Val-Ala-Asp-AFC)	Cysteine protease (caspase 1-like)	Colony	+/+	+/+	+/+	−/−
		Zone	+/+	+/+	+/+

^aCellulose acetate membranes, containing substrates with different peptidyl side groups linked to fluorogenic 7-amino-4-trifluoromethylcoumarin (AFC) as the leaving group, were overlaid onto P. piscicida colonies, zones of clearing around the colonies, and lawns of healthy V. vulnificus cells outside the areas of inhibition. Fluorescence produced by (i) enzymatic activity from the colonies, (ii) the clear zones of Vibrio inhibition around the colonies, and (iii) lawns of Vibrio outside the zones of inhibition were recorded as positive (+) or negative (−) fluorescence after 15 min and 1 h.

^bShown as the catalog number (Enzyme Systems Products, Livermore, CA), followed by the name of the substrate.