Abstract
PLA~2~ is a diverse class of enzymes with a broad spectrum of physiological functions. Secretory PLA~2~ isoforms have been reported to exhibit important innate immune function in higher vertebrates. This study was conducted to characterize PLA~2~ activity in the serum of the American alligator (Alligator mississippiensis). We used a glycerophospholipid with a fatty acid in the sn‐2 position labeled with a fluorescent probe (BODIPY) to detect and quantify alligator serum PLA~2~ activity. Incubation of BODIPY‐labeled bacteria with different concentrations of alligator serum resulted in a concentration‐dependent detection of PLA~2~ activity. Kinetic studies showed that product formation was rapid, with substantial activity within 5 min, and maximal activity at approximately 20 min. The alligator PLA~2~ activity was temperature‐dependent, with activity at lower temperatures (5−10°C) approximately half of that observed at temperatures of 30–40°C. In addition, the generation of fluorescent product was reduced by a specific inhibitor (p‐bromophenacyl bromide) of secretory PLA~2~ in a concentration‐dependent manner, enforcing the idea that the observed activities are due to a secretory PLA~2~ enzyme in alligator serum. J. Exp. Zool. 311A: 662–666, 2009. © 2009 Wiley‐Liss, Inc.