Ortho-Tyrosine in an Insect Cuticle

Abstract

AN examination of a developing insect cuticle by means of paper partition chromatography has shown that the changes taking place in amino-acid compostion primarily concern the aromatic members. Larval cuticles of Calliphora vomitoria have been hydrolysed at different stages of development in 6 N hydrochloric acid and chromatograms developed using butanol/acetic acid/water and phenol saturated with water as solvents. The positions of the amino-acid spots were located by spraying with ninhydrin. At all stages the following amino-acids were recognized: alanine, arginine, glutamic acid, glycine, leucine, lysine, proline, serine, threonine, and valine. In addition, tryptophan is present before the onset of puparium formation. The chief differences between the various developmental stages concern the presence or absence of phenylalanine and para-tyrosine. At the concentration of hydrolysate used, phenylalanine is only very faintly distinguishable in the cuticles of four- and five-day old larvæ; but in the seven-day old and white puparial cuticles it is abundant. Thereafter, however, in the one day old and fully hardened puparia, it is absent. Somewhat similarly, para-tyrosine is present at all stages up to, and including, the white puparium, but is absent from the hardened puparial cuticle.