Comparative composition of free,peptide and protein amino acids in symbiotic and aposymbiotic Sitophilus oryzae (coleoptera,curculionidae)

Free, peptide-bound and total amino acids were determined in symbiotic and aposymbiotic Sitophilus oryzae. The concentrations of free and peptide amino acids were higher, that of protein amino acids lower in aposymbiotic larvae (+30, +66 and −35%, respectively). In the free fraction, tyrosine concentration was the only one to be lower in aposymbiotic larvae (−41%) and could be a limiting factor for protein synthesis.In nymphs and adults, the compositions in symbiotic and aposymbiotic insects were very similar. A deficiency of tyrosine occurred however in aposymbiotic nymphs and of aspartate, glutamate, arginine, lysine and tyrosine in aposymbiotic adults. On the other hand, the composition in ovaries was unchanged.It is suggested that symbiotes could favour the synthesis of proteins in the larvae by increasing the efficiency of the conversion of phenylalanine in tyrosine.