ASSOCIATION BETWEEN CHITIN SYNTHESIS AND PROTEIN SYNTHESIS IN THE SHRIMP PENAEUS VANNAMEI

Abstract

ABSTRACT The synthesis of chitin, the major structural polysaccharide of the arthropod cuticle, has been examined in postlarval stages of the commercial shrimp Penaeus vannamei. Analysis of the cuticle revealed 73% (by weight) amino acids and 27% N-acetylglucosamine. Major amino acids in the cuticle are Asx (aspartic acid and asparagine), Glx (glutamic acid and glutamine), Thr, Ala, His, and Leu. Metabolic labeling studies were carried out with a variety of radiolabeled amino acids. The kinetics of amino acid incorporation into the cuticle reveal a burst of incorporation at 30 min of incubation followed by a decrease in 60 min, and finally a linear increase of incorporation up to 120 min. Incorporation of 'H glucosamine into the cuticle is linear over the 3 h period. Incubation of postlarval Penaeus with puromycin decreases synthesis of soluble proteins 90% as measured by incorporation of several labeled amino acids. Incorporation of radiolabeled amino acids into the insoluble cuticle residue is blocked 90% by puromycin. Incorporation of 3H D-glucosamine into the cuticle is also blocked 90% by puromycin. These data support the hypothesis that crustacean chitin is secreted as a glycoprotein complex and that concurrent protein synthesis is required for chitin deposition to continue.