The effects of hydroxylamine and tyrosine on homogenatesof early Drosophila pupae have been studied by several criteria.Both low speed and high speed supernatants of thehomogenized pupae give positive tests for hydroxamic acidsafter incubation with hydroxylamine. A comparison of thehydroxamic acid forming abilities of the supernatants showsthat the low speed supernatant is the more active and thattyrosine increases hydroxamate formation in the low speedbut not in the high speed supernatants.
Both hydroxylamine and tyrosine have definite effectson alkaline phosphatase activity in the low speed supernatant.Tryosine causes an increase in the activity upon incubationat 0°C and 25°C. Hydroxylamine decreases the activity regardlessof the temperature or the presence of tyrosine.
Both tyrosine and hydroxylamine affect the distributionof ninhydrin-positive compounds of dialyzates of low speedsupernatants. Hydroxylamine effectively reduces the amountof the acidic components, but its effect is slightly modifiedby tyrosine. The presence of tyrosine alone increases theamount of acidic materials as compared to the untreated sample.In general, the ninhydrin-positive compounds are more sensitiveto the presence of hydroxylamine than of tyrosine.
Some preliminary work on the nature of the compounds inquestion shows that they contain more than one amino acid.The data on the nature of these compounds is consistent withthe proposition that peptidyl hydroxamates are the Fe ^(+++)-positive materials.
Naturally-occurring peptides and the current understandingof protein synthesis are reviewed. The possibility thatpeptides per se are incorporated into the proteins in Drosophilapupae is discussed and mechanisms for this possibilityare explored.
