Matsui C, Koyata H, Hiraga K
Department of Biochemistry, Toyama Medical and Pharmaceutical University School of Medicine, Japan.
Arch Biochem Biophys. 1993 Jan;300(1):69-74. doi: 10.1006/abbi.1993.1010.
The hepatic glycine cleavage system in the chicken was examined at different stages of development to study regulation of its biosynthesis. Embryonic levels of polypeptide and mRNA for glycine decarboxylase, one of the three intrinsic components of this enzyme system, were approximately 10% of their adult levels and were rapidly increased following hatching. Those of H-protein, another intrinsic component, were somewhat higher and were more slowly increased throughout the course of development. The change in activities of the two components went with the increase in their polypeptide levels. Moreover, both relative levels of mRNAs for the two components and relative efficiencies of transcription of their genes were not constant during development. T-protein biosynthesis appeared to follow a course similar to that of H-protein. These observations imply that during development, the production of H-protein and T-protein is regulated by similar mechanisms. Further, it is likely that the same mechanisms do not direct the regulatory processes in the biosynthesis of glycine decarboxylase and that embryo and adult livers possess different regulatory modes regarding the biosynthesis of this enzyme system. The shift to the adult mode appeared to occur at birth. The glycine cleavage activity that was three times higher than that in 12-day-old embryo was observed in adult liver mitochondria.
研究鸡肝脏甘氨酸裂解系统在不同发育阶段的生物合成调控。该酶系统的三个内在组分之一甘氨酸脱羧酶的多肽和mRNA的胚胎水平约为成年水平的10%，孵化后迅速增加。另一个内在组分H蛋白的水平略高，在整个发育过程中增加较慢。这两个组分活性的变化与它们多肽水平的增加一致。此外，这两个组分mRNA的相对水平及其基因转录的相对效率在发育过程中并非恒定。T蛋白的生物合成似乎与H蛋白遵循相似的过程。这些观察结果表明，在发育过程中，H蛋白和T蛋白的产生受相似机制调控。此外，指导甘氨酸脱羧酶生物合成调控过程的机制可能不同，胚胎肝脏和成年肝脏在该酶系统生物合成方面具有不同的调控模式。向成年模式的转变似乎发生在出生时。在成年肝脏线粒体中观察到甘氨酸裂解活性比12日龄胚胎高3倍。
