In fish, the innate immune system is more important than the adaptive immune system because it responds quickly and nonspecifically to protect against pathogens. Thus, a variety of innate immune molecules have been found in fish. Recently, l-amino acid oxidases (LAOs) were discovered as a new member of the antibacterial protein from fish skin mucus and serum. In this study, we newly found an antibacterial LAO in red-spotted grouper (Epinephelus akaara) serum. It showed a broad range of substrate specificity with aromatic and hydrophobic amino acids. The grouper LAO gene had a low expression level in the kidney under normal conditions; however, it was significantly upregulated by blood loss 1 day after bleeding. In addition, the LAO activity in the serum recovered within 3 days in the same experiment. This quick recovery may indicate that the LAO is an essential innate immune molecule in the whole grouper body.

在鱼类中，先天免疫系统比适应性免疫系统更重要，因为它可以快速且非特异性地反应以抵御病原体。因此，在鱼类中发现了多种先天免疫分子。最近， L-氨基酸氧化酶（ LAOs）被发现是鱼皮粘液和血清中抗菌蛋白的新成员。在这项研究中，我们在红斑石斑鱼（Epinephelus akaara ）中新发现了一种抗菌 LAO) 血清。它对芳香族和疏水性氨基酸表现出广泛的底物特异性。石斑鱼LAO基因在正常情况下在肾脏中表达水平较低；然而，出血后1天失血显着上调。此外，在同一实验中，血清中的 LAO 活性在 3 天内恢复。这种快速恢复可能表明LAO是整个石斑鱼体内必不可少的先天免疫分子。