Constitutive enzymes of the developing chick embryo: adenosine deaminase

Abstract

Adenosine deaminase activity/milligram of protein does not vary significantly in homogenates of the whole chick embryo after 2 days of incubation or of its yolk sac from 2 to 14 days of incubation or in the liver from 7 days of incubation to 34 weeks after hatching. Adenosine was injected into eggs at from 1 to 8 days of incubation but no significant increase of adenosine deaminase activity in homogenates of the whole chick embryo or yolk sac was observed at 24 hr. after each injection. Five successive doses of 10 mg of adenosine injected at 24 hr.-intervals into 6-day-old embryos produced no increased adenosine deaminase activity in the livers of the embryos removed 24 hr. after the last dose. Liver adenosine deaminase was not significantly increased by single or multiple injections of adenosine into embryos during 6-8 days of incubation or by similar injections into chicks or fowls. Adenosine deaminase activity was chiefly localized in the supernatant fraction of a liver homogenate of a 34-week-old cockerel and its optimum activity in this fraction was at pH 7.0. Adenosine deaminase activity/ milligram of protein was similar in embryonic and cockerel liver, whole chick embryos and yolk sacs. It is concluded from these results that adenosine deaminase is a constitutive and not an adaptive enzyme throughout the development of the chick.