Developmental Aspects of Tyrosine Metabolism

Abstract

The developmental patterns of the enzymes involved in the metabolic degradation of tyrosine in rat Liver , tyrosine

transaminase, p-hydroxyphenylpyruvate hydroxylase, h'omogenti-

sate oxygenase, maleylacetoacetate isomerase and fumarylaceto-

acetate hydrolase 'were studied during the first 24 hours after

birth. Except for tyrosine transaminase, all were quite active

at birth. The developmental changes indicated that the trans-

aminase, isomerase, and hydrolase did not appear to show

coordinated patterns in this time-period. However, the

hydroxylase and oxygenase appeared to be coordinated in I their development, an observation Vlhich is consistent with

the results of the analysis of variance. With the exception

of the isomerase, each enzyme showed a peak of activity at

somepoint in the 24 hours; these peaks appeared to be timed

in the reverse of the metabolic sequence. The first enzyme of the metabolic sequence (transaminase) had the lowest activity at most times, the last enzyme (hydrolase) had the highest activity, with the remaining three enzymes falling in between these extremes. No satisfactory explanation is available for the very hih activity of the hydrolase