In fishes, such as zebrafish and rainbow trout,
cathepsin L is known to be involved in oogenesis and
embryogenesis (Li et al. 2010, 2011). It has also been
reported that cathepsin L is highly up-regulated in
haemopoietic tissues including liver, kidney and blood
during bacterial and viral infection in fishes (Aranishi
et al. 1997; Yeh & Klesius 2009; Ahn et al. 2010; Chen
et al. 2011), which clearly indicates the immunological
role of cathepsin L in fishes. Cathepsin L in fish shows a
strong proteolytic activity for several proteins including
myofibrillar proteins in muscles of Oncorhynchus keta
(Yamashita & Konagaya 1990), Scomber japonicas (Lee
et al. 1993), Engraulis japonica and Atheresthes stomias
(Visessanguan et al. 2003) suggesting its participation
in intracellular and extracellular protein catabolism in
fish (Aranishi et al. 1997). Cathepsin L is present in
fish mucus and it is reported to produce antimicrobial
peptides during infection (Lee et al. 1993)