Thureen P J, Narkewicz M R, Battaglia F C, Tjoa S, Fennessey P V
Department of Pediatrics, University of Colorado Health Sciences Center, Denver 80262, USA.
Pediatr Res. 1995 Nov;38(5):775-82. doi: 10.1203/00006450-199511000-00023.
Previous in vivo studies in the ovine fetus have demonstrated net serine production by the fetal liver, a pattern not seen in the adult sheep. The goal of this study was to determine the major metabolic pathways responsible for fetal hepatic serine production by using stable isotope methodology in primary culture of late gestation ovine fetal hepatocytes. Specifically selected tracers of glycine were added to individual cultures, with production of labeled serine determined after 24 h of incubation. When [1-13C1]glycine or [2-13C1]glycine was used as the initial tracer, serine enrichment at 24 h indicated that approximately 30% of serine production comes from glycine. Quantitative comparison of serine enrichment from these two tracers suggests that serine synthesis from glycine occurs via the combined action of the glycine cleavage enzyme system (GCE) and serine hydroxymethyltransferase (SHMT). Using [1,2-13C2(15)N1]glycine as the tracer, there was no significant increase in M + 2 glycine in the medium over 24 h, suggesting no reversible transamination of glycine, and therefore no significant movement of glycine through the glyoxalate pathway. These data demonstrate that in primary culture of fetal ovine hepatocytes, approximately 30% of serine biosynthesis is derived from glycine, primarily via the combined action of GCE and SHMT.
先前在绵羊胎儿体内进行的研究表明，胎儿肝脏有净丝氨酸生成，而成年绵羊则没有这种模式。本研究的目的是通过在妊娠晚期绵羊胎儿肝细胞原代培养中使用稳定同位素方法，确定胎儿肝脏丝氨酸生成的主要代谢途径。将经过特别挑选的甘氨酸示踪剂添加到各个培养物中，孵育24小时后测定标记丝氨酸的生成情况。当使用[1-¹³C₁]甘氨酸或[2-¹³C₁]甘氨酸作为初始示踪剂时，24小时时丝氨酸的富集情况表明，约30%的丝氨酸生成来自甘氨酸。对这两种示踪剂的丝氨酸富集情况进行定量比较表明，甘氨酸合成丝氨酸是通过甘氨酸裂解酶系统（GCE）和丝氨酸羟甲基转移酶（SHMT）的联合作用实现的。使用[1,2-¹³C₂(¹⁵)N₁]甘氨酸作为示踪剂时，培养基中M + 2甘氨酸在24小时内没有显著增加，这表明甘氨酸没有可逆转氨作用，因此甘氨酸没有通过乙醛酸途径发生显著移动。这些数据表明，在绵羊胎儿肝细胞原代培养中，约30%的丝氨酸生物合成来自甘氨酸，主要是通过GCE和SHMT的联合作用。
