ASPARTIC AND CYSTEINE PEPTIDASES IN THE LARVAL DEVELOPMENT OF Penaeus vannamei: EXPRESSION AND ACTIVITY PROFILES

Peptidases are hydrolases that cleave peptide bonds within proteins , they are classified in four  main classes: serine-, aspartic-, cysteine- and metallopeptidases, according to the mechanism of proteolysis. Aspartic and cysteine peptidases are multifunctional enzymes, their relevance in larval development has been recognized in several arthropod species, including crustacean s, and  mainly described as triggers of molting and metamorphosis, as well as fat body dissociation and tissue remodeling. However , its relevance is poorly understood in  P. vannamei , the most valuable resource in crustacean aquaculture for which descriptions of the molecular mechanisms of many important physiological conditions including larval development are rather poor .  In this work the  cysteine and aspartic activity profiles along the larvae development of P . vannamei was determined at transcript and activity levels, the gene expression of  5 cysteine and 1 aspartic peptidase was assesed by qPCR. Since changes in mRNA abundance do not necessarily correlate with the corresponding mature protein products, the cysteine and aspartic proteolytic activity was also assessed using fluorogenic substrates designed to be recogn ized  by  such peptidase classes.

Our results indicate that both, cysteine and aspartic peptidases are expressed  along the  P. vannamei larval development , and  they  seem to be particularly relevant during early stages of development, since peaks of activity were detected during nauplii and zoea stages;  presumably cathepsin L, C, and  calpain are the responsible for cysteine peptidase activity since their transcripts were higher at early stages. Aspartic peptidase activity was also detected at early stages but  the corresponding transcript (cathepsin D) is predominantly expressed at mysis stages, although  detected in all larval stages  at  a  lower rate.

Conclusions: The profiles of mRNA expression and enzymatic activity of cysteine and aspartic peptidases indicate that they are controlled orderly and play multiple roles during larval development in  shrimp. The data presented here contribute to understanding the proteolytic dynamics occurring  during P . vannamei larvae development.