Hashimoto Y, Abe M, Kiuchi Y, Suzuki A, Yamakawa T
J Biochem. 1984 Jun;95(6):1543-9. doi: 10.1093/oxfordjournals.jbchem.a134766.
GM2 containing NeuGc was a major ganglioside in the liver of mouse strains such as BALB/c, DBA/2, C3H/He, and C57BL/10, whereas WHT/Ht mouse liver did not contain GM2(NeuGc) but contained GM3(NeuGc) as a major ganglioside. Since GM3(NeuGc) is a biosynthetic precursor of GM2(NeuGc), WHT/Ht liver was considered to lack the ability to synthesize GM2(NeuGc) from GM3(NeuGc) (Hashimoto, Y., et al. (1983) J. Biochem. 93, 895-901). In this study we measured the activity of UDP-N-acetylgalactosamine : GM3(NeuGc) N-acetylgalactosaminyltransferase in the liver of BALB/c, WHT/Ht, and their progeny. The transferase activity in the microsomal fraction of BALB/c liver was 2.10 +/- 0.32 X 10(-5) units/mg protein (means +/- S.D.), whereas no activity was detected in that of WHT/Ht liver, F1 hybrids between BALB/c and WHT/Ht expressed GM2(NeuGc) as well as the enzyme activity, the level of which was almost half that in BALB/c liver 1.10 +/- 0.12 X 10(-5) units/mg protein). The backcross generation of F1 to WHT/Ht segregated into two groups with respect to expression of GM2(NeuGc) and the transferase activity: 11 of the 21 mice analyzed expressed both GM2(NeuGc) and the transferase activity (1.28 +/- 0.18 X 10(-5) units/mg protein), whereas the rest expressed neither. These results suggest that the expression of GM2(NeuGc) is directly regulated by the activity of UDP-N-acetylgalactosamine: GM3(NeuGc) N-acetylgalactosaminyltransferase in mouse liver.
含有NeuGc的GM2是BALB/c、DBA/2、C3H/He和C57BL/10等小鼠品系肝脏中的主要神经节苷脂，而WHT/Ht小鼠肝脏不含GM2(NeuGc)，但含有GM3(NeuGc)作为主要神经节苷脂。由于GM3(NeuGc)是GM2(NeuGc)的生物合成前体，因此认为WHT/Ht肝脏缺乏从GM3(NeuGc)合成GM2(NeuGc)的能力（Hashimoto, Y.,等人(1983)《生物化学杂志》93, 895 - 901）。在本研究中，我们测定了BALB/c、WHT/Ht及其后代肝脏中UDP-N-乙酰半乳糖胺:GM3(NeuGc) N-乙酰半乳糖胺基转移酶的活性。BALB/c肝脏微粒体部分的转移酶活性为2.10±0.32×10(-5)单位/毫克蛋白质（平均值±标准差），而在WHT/Ht肝脏中未检测到活性，BALB/c和WHT/Ht之间的F1杂种同时表达GM2(NeuGc)和酶活性，其水平几乎是BALB/c肝脏的一半，为1.10±0.12×10(-5)单位/毫克蛋白质）。F1与WHT/Ht的回交后代在GM2(NeuGc)表达和转移酶活性方面分为两组：在分析的21只小鼠中，有11只同时表达GM2(NeuGc)和转移酶活性（1.28±0.18×10(-5)单位/毫克蛋白质），而其余小鼠均不表达。这些结果表明，GM2(NeuGc)的表达直接受小鼠肝脏中UDP-N-乙酰半乳糖胺:GM3(NeuGc) N-乙酰半乳糖胺基转移酶活性的调节。
