Activity of trypsin from Litopenaeus vannamei

The trypsin of Litopenaeus vannamei is a polymorphic molecule. Three sequences are translated in the digestive gland of this species. In some individuals, there are 2 isozyme forms and others have 3 that form 3 trypsin phenotypes. Changes in the activity of trypsin do not occur because they turn off or on a specific isozyme, but the changes appear to be related to changes in the rate of transcription of the established isozymes. Trypsin activity is modulated by genetic factors and the type of food during ontogeny. During this period L. vannamei has a change in trypsin activity, before any other decapods, during which they become carnivorous. The process of molt occurs through defined metabolic changes that affect trypsin activity. The lowest trypsin activity occurs in the D3 and A-B stages and the highest during the D_1`` D_1``` stages. Successfully validated trypsin activity detected in feces follows the trypsin activity in the digestive gland in individuals. Using this technique, we found that stress caused by changes in the protein content in feed and by manipulation influences the trypsin activity in juvenile L. vannamei. Trypsin activity can be modulated during a feeding cycle. Organisms that feed once a day show a decrease in trypsin activity after feeding and an increase 2 h prior to the next feeding. This occurs whether they are fed at 2200 or at 1200 h, suggesting a real regulation caused by the time of feeding. If trypsin activity is modulated at the transcriptional level and individual isozyme activity differs among the 3 isozymes, the 3 phenotypes could yield a different biological response to improve feed conversion or growth of the organism during culture.