Lactic and malic dehydrogenases in the developing chick embryo.

A study of the activity and distribution of glutamic dehydrogenase in various tissues of the developing chick embryo has recently been made (Solomon, 1957). It was found that glutamic dehydrogenase showed marked fluctuations of activity in certain tissues at various stages of development. However, as only relatively low amounts of the enzyme were found in all tissues of the chick embryo and fowl, the formation of glutamic acid from carbohydrate sources via the citric acid cycle did not appear to be an important metabolic route in avian tissue. A similar study is reported here on lactic dehydrogenase and malic dehydrogenase, which are both pyridine nucleotidedependent and utilize homologous keto acids as substrates. The activity of lactic dehydrogenase and malic dehydrogenase in the very early chick embryo has not been measured, and it was not known whether chick blastoderms possessed relatively high amounts of these enzymes, as was found to be the case for glutamic dehydrogenase (Solomon, 1957). Sachs, Ephrussi & Rapkine (1933) found that lactic, succinic and citric dehydrogenases were present in extracts of 8-day-old chick embryos. Booth (1935) could not detect lactic dehydrogenase in the chick embryo until after 8 days' incubation but found that some of the enzyme was present in the yolk