Iurovitskii Iu G, Krivopishin I P, Mil'man L S
Biokhimiia. 1978 Sep;43(9):1602-15.
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.
在鸡胚肝脏个体发育的各个阶段，糖原磷酸化酶（EC 2.4.1.1）由一种同工酶代表，其性质与同工酶IL或F相近。从发育第8天到孵化，总酶活性（a + b形式）逐渐增加1.5倍，在胚胎发育结束时观察到酶的几乎完全激活。磷酸化酶b在1 mM AMP存在下具有高催化活性，并且被鱼精蛋白和0.2 M Na2SO4激活。糖原合成酶（EC 2.4.1.11）在个体发育过程中具有恒定的Km（UDFG）值。在存在10 mM葡萄糖-6-磷酸的情况下，该值对于酶I型和D型均约为5×10^(-4) M。总酶活性在胚胎后第17天达到最大值，此后降低超过6倍。在胚胎发育过程中，I/D比值从发育第8天的0.2增加到糖原大量积累期间的0.45，并在孵化前降至0.33。胚胎肝脏中的糖原生物合成与I/D比值的增加密切相关，即酶的活性形式增加。胚胎肝脏中颗粒状糖原的比例在发育第8天至14天之间从总糖原含量的15％增加到90％。颗粒状糖原中所含糖原合成酶的活性从8日龄胚胎中的40％增加到18日龄胚胎中的90％。仅在胚胎发育的第12天在颗粒状糖原中发现磷酸化酶的活性，并且仅在发育的第19天达到其最大值（总酶活性的80％）。得出的结论是，成年鸡肝脏中保留了胚胎酶——糖原磷酸化酶和糖原合成酶。
