Effect of dopa-decarboxylase inhibition on the metabolism of β-alanyl- l-tyrosine during puparium formation in the fleshfly Sarcophaga bullata parker

Abstract

1. 1. The metabolism of the dipeptide β-alanyl- l-tyrosine has been studied in the newly formed white pupa of the fleshfly Sarcophaga bullata injected with a potent DOPA-decarboxylase inhibitor, ( dl)-3-(3,4-dihydroxyphenyl)-2-hydrazino-2-methylpropionic acid (abbr. α-MDH). Low levels of α-MDH (5 μg/individual) completely inhibited hardening and darkening (sclerotization) of the puparium. 2. 2. Marked decreases in β-alanyl- l-tyrosine levels were accompanied by nearly equimolar increases in the levels of free β-alanine and tyrosine plus DOPA during α-MDH inhibition. In controls the dipeptide also disappeared rapidly, but the level of free β-alanine remained nearly constant and that of tyrosine fell sharply. DOPA was undetected in the controls. 3. 3. These results are consistent with the hypothesis that during pupal sclerotization in Sarcophaga, most, if not all, of β-alanyl- l-tyrosine is cleaved to its free amino acids followed by their individual metabolism and incorporation into cuticle structure.