INCORPORATION OF VARIOUS PUTATIVE PRECURSORS INTO CUTICULAR 3,4-DIHYDROXYPHENYLACETIC ACID OF ADULT TENEBRIO-MOLITOR

Post-emergence levels of 3,4-dihydroxyphenylacetic acid (DOPAC) and ketocatechol were determined in cuticle from adult Tenebrio molitor. Possible pathways for biosynthesis of DOPAC were studied by comparing the incorporation of injected [U-14C]tyrosine, [7-14C]dopamine, [7-14C]DOPA, [7-14C]tyramine, [U-14C]p-hydroxyphenylpyruvic acid (p-HPPA) and [ring-3H]p-hydroxyphenylacetic acid (p-HPAA) into cuticular DOPAC during its period of maximal increase 1-3 days after adult emergence. Increased incorporation of [U-14C]tyrosine between days 0 and 3 suggests rapid de novo biosynthesis of DOPAC from this primary precursor. Of the putative intermediates tested, only p-HPPA had a pattern of incorporation similar to that seen with tyrosine. Since p-HPAA was poorly incorporated into both cuticle and DOPAC, a tentative pathway tyrosine → p-HPPA → 3,4-dihydroxyphenylpyruvic acid → DOPAC is proposed. © 1990.