Regulation of glycolysis by a novel brain-type isozyme of fructose 6-phosphate 2kinase/fructose 2,6-bisphosphatase

果糖6-磷酸2-激酶/果糖2,6-二磷酸酶催化果糖2,6-二磷酸的合成和降解，果糖2,6-二磷酸是糖酵解最有效的活化剂。我们之前已经发现了编码一种新型脑型同工酶催化核心结构域的部分cDNA （RB7）。为了阐明RB7 cDNA的全长序列，我们利用3′和5′快速扩增cDNA末端法进行了cDNA克隆，并从大鼠脑中分离了8个同种异构体。编码5′-非翻译区、氨基末端结构域和催化核心结构域的cDNA序列在所有同工异构体中是相同的。然而，通过序列分析发现羧基端存在异质性。这种异质性不是由多个基因的转录引起的，因为Southern blot和基因组序列分析显示该基因在大鼠基因组中是一个拷贝。这些转录本很可能代表了基因的剪接变体。该基因在骨骼肌中也有高水平的表达。然而，选择性剪接的模式与大脑不同，在骨骼肌中只检测到四种同种异构体。

Fructose 6-phospate, 2-kinase/fructose 2,6-bisphosphatase catalyzes the synthesis and degradation of fructose 2,6-bisphosphate, which is the most potent activator of glycolysis. We have shown previouslt the occurrence of a partial cDNA (RB7) encoding the catalytic core domain of a novel brain type isozyme. To elucidate the full-length sequence of RB7 cDNA,we have carried out cDNA cloning using 3'- and 5'- rapid amplification cDNA ends method and have isolated eight isoforms from rat brain. The cDNA sequences encoding the 5'-untranslated region, the amino-terminal domain, and the catalytic core domain were identical among all th isoforms. However, heterogeneity of the carboxyl-terminus was found by sequence analysis. This heterogeneity was shown not to have resulted from transcription of multiple genes, as Southern blot and genomic sequence analysis revealed that the gene was a single copy in the rat genome. It is likely that these transcripts represent splice variants of the gene. High-level expression of the gene was also observed northern blot analysis in skeletal muscle. However, the pattern of alternative splicing was different from that of brain, and only four isoforms were detected in skeletal muscle.