[Glycogen metabolic enzymes in the skeletal muscles of the developing chick embryo]. / Fermenty obmena glikogena v skeletnykh myshtsakh razvivaiushchegosia zarodysha kuritsy.

In the skeletal muscles of the chick embryo from the 10th till the 15th day of embryogenesis, phosphorylase (EC. 2.4.1.1) is represented by two isozymes one of which corresponds, by electrophoretic mobility, to the liver phosphorylase and another to phosphorylase of the skeletal muscles of the adult rat. From the 17th day of embryogenesis on only one isozyme of phosphorylase is found in the skeletal muscles which is identical with that of the skeletal muscles of the adult bird. The isozyme spectrum of phosphorylase of the whole 4 days old embryo contains, besides phosphorylase L, a special "embryonic" isozyme which differs from that of the skeletal muscles by immunochemical characteristics and electrophoretic mobility. From the 10th day of embryogenesis till hatching, the activity of phosphorylase of the skeletal muscles increases more than 50 times and that of glycogen synthetase (EC. 2.4.1.11) only 4 times.

[Glycogen phosphorylase isoenzymatic makeup changes in the liver of birds and mammals in ontogeny]. / Izmeneniia izofermentnogo sostava glikogen fosforilazy v pecheni ptits i mlekopitaiushchikh v ontogeneze.

It was established by means of immunochemical titration that phosphorylase of the chickliver, beginning from the 8th day of embryogenesis, was represented by an isozyme, immunochemically identical or closely related to mammalian phosphorylase L. At the early stage of development (4th day) the chick embryo contained both isozyme L (ca. 60%) and isozyme, closely related to mammalian isozyme I. In the liver of 15 days old rat embryos the ratio of isozymes I and L equaled 1 : 2. It is suggested that the ratio of L and IL is close to 1 : 1. The isozyme IL is replaced for the isozyme L completely during the second ten day period of postnatal development.

[Enzymes of glycogen metabolism in chick embryo liver]. / Fermenty obmena glikogena v pecheni embriona tsyplenka.

At all stages of ontogenesis glycogen phosphorylase (EC 2.4.1.1) from liver chick embryos in represented by an isoenzyme whose properties are close to those of isoenzyme IL or F. Total enzyme activity (a+b forms) from the 8th day of development up to hatching gradually increases 1.5-fold, a practically complete activation of enzyme being observed by the end of embryogenesis. Phosphorylase b possesses high catalytic activity in the presence of 1 mM AMP and it activated by protamine and 0.2 M Na2SO4. Glycogen synthetase (EC 2.4.1.11) has a constant Km(UDFG) value during ontogenesis. This value is about 5.10(-4) M in the presence of 10 mM glucose-6-phosphate, both for I- and D-forms of enzyme. The total enzyme activity reaches its maximum on the 17th postembryonic day and is decreased more than 6-fold thereafter. In the course of embryogenesis the I/D ratio is increased from 0.2 on the 8th day of development up to 0,45 during extensive accumulation of glycogen and falls down to 0.33 before hatching. Glycogen biosynthesis in embryonic liver is wellcorrelated with the increase in the I/D ratio, i.e. the increase of the active form of enzyme. The proportion of granular glycogen in embryonic liver is increased from 15% up to 90% of total glycogen content between the 8th and 14th days of development. The activity of glycogen synthetase contained in granular glycogen is increased from 40% in the 8-day-old embryos up to 90% in the 18-day-old ones. The activity of phosphorylase is found in granular glycogen only on the 12th day of embryogenesis and reaches its maximum (80% of total enzyme activity) only on the 19th days of development. It is concluded that in the adult chicken liver the embronic enzymes--glycogen phosphorylase and glycogen synthetase--are retained.

[Changes in glycogen metabolism in chick embryo liver in relation to the formation of glycosomes]. / Izmeneniia obmena glikogena v pecheni kurinogo zarodysha v sviazi s formirovaniem glikosom.

In the chick embryo liver the portion of granular glycogen increases from 15 to 90% of the total content during the period from the 8th till the 14th days of developments. The activity of glycogen synthetase (KF 2.4.1.11) localized in the fraction of granular glycogen increases from 40 to 90% of the total activity in the 18 days old embryo. The activity of phosphorylase (KF 2.4.1.1) is detected in the granular glycogen of the liver only on the 12th day of development (10% of the total activity) and increase up to 80% on the 19th day of development. The maximal activation of glycogen synthetase and phosphorylase is noted after the glycosomes of formation in the developing embryoliver. A suggestion is put forward to the effect that the process of glycosome formation is a factor of the control of glycogen synthetase and phosphorylase activity.

[Correlation of active and inactive forms of phosphorylase and glycogen synthetase in the liver of the developing chick embryo]. / Sootnoshenie aktivnoi i neaktivnoi form fosforilazy i glikogensintetazy v pecheni razvivaiushchegosia zarodysha kuritsy.

The marked changes in the activity and ratio of the active and inactive forms of glycogen synthetase and phosphorylase were found in the liver of developing chick embryo. The activity of phosphorylase increased in the liver from the 8th day of incubation till the end of embryogenesis. The practically complete activation of the inactive form of this enzyme was noted in the end of embryogenesis. The activity of glycogen synthetase in the liver increased till the 17th day of incubation and sharply decreased more than 6 times thereafter. The maximum of the active form of glycogen synthetase (1/3 of total activity) was noted on the 17th day as well. The changes in the content of glycogen synthetase in the liver are synchronized with those in the activity and ratio of the active and inactive forms of glycogen synthetase. The role of changes in the concentration of glucose and glucose-6-phosphate in the control of ratio of the active and inactive forms of enzymes of glycogen metabolism is discussed.