Sarcophagine (beta-alanyl-L-tyrosine) synthesis in the fat body of Sarcophaga peregrina larvae.

The fat body of Sarcophaga peregrina larvae was found to have activity for synthesis of sarcophagine (beta-alanyl-L-tyrosine). This activity was due to a soluble enzyme (sarcophagine synthetase) that requires Mg2+ and ATP as cofactors. The enzyme activity decreased significantly after puparium formation and no sarcophagine synthesis was detected when fat body from white pupae was incubated in vitro with 3H-beta-alanine. This apparent loss of sarcophagine synthesis was found to be partly due to peptidase, which was induced in the fat body after puparium formation. The activity of sarcophagine synthetase itself in the lysate of pupal fat body, however, was found to be significantly lower than that in the lysate of larval fat body, suggesting the presence of a developmentally regulated mechanism of sarcophagine production.