Mizunuma H, Tashima Y
Akita University College of Allied Medical Science, Japan.
Eur J Biochem. 1994 Oct 1;225(1):433-9. doi: 10.1111/j.1432-1033.1994.00433.x.
Fructose 1,6-bisphosphatase mRNA and enzyme activity in HL-60 cells were rapidly and markedly induced by calcitriol (formerly known as 1 alpha,25-dihydroxyvitamin D3). The activity reached 70-80 times the basal level after 96 h. The enzyme activity in the cells incubated for 96 h with calcitriol decreased immediately after its withdrawal but after a 24-h incubation the activity in the cells continued to increase slightly and then decreased slowly. Calcitriol increased the enzyme activity dose-dependently with maximal stimulation at 10 nM and half-maximal at 2.1 nM. The rate of synthesis of fructose 1,6-bisphosphatase almost paralleled the increase in mRNA level during treatment with calcitriol. When calcitriol was removed from media after incubation for either 24 h or 96 h, fructose-1,6-bisphosphatase mRNA and fructose-1,6-bisphosphatase synthesis decreased rapidly to the basal level. The enzyme was only slightly degraded in the cells incubated with calcitriol for 24 h followed by the subsequent culture without calcitriol but it was degraded with a half-life estimated to be approximately 64 h in the same cells followed by culturing with calcitriol. In the cells incubated for 96 h, the same degradation rate (i.e. half-life approximately 64 h) was observed irrespective of the following culture with or without calcitriol. Calcitriol did not affect the degradation rate of total soluble proteins.
1,6-二磷酸果糖磷酸酶的mRNA及酶活性在HL-60细胞中可被骨化三醇（以前称为1α,25-二羟基维生素D3）迅速且显著地诱导。96小时后，该活性达到基础水平的70 - 80倍。用骨化三醇孵育96小时的细胞，在撤除骨化三醇后，酶活性立即下降，但在24小时孵育后，细胞中的活性仍略有增加，随后缓慢下降。骨化三醇呈剂量依赖性地增加酶活性，在10 nM时达到最大刺激，在2.1 nM时达到半数最大刺激。在骨化三醇处理期间，1,6-二磷酸果糖磷酸酶的合成速率几乎与mRNA水平的增加平行。当在孵育24小时或96小时后从培养基中去除骨化三醇时，1,6-二磷酸果糖磷酸酶的mRNA和1,6-二磷酸果糖磷酸酶的合成迅速降至基础水平。在用骨化三醇孵育24小时随后在无骨化三醇的条件下继续培养的细胞中，该酶仅轻微降解，但在相同细胞中用骨化三醇培养后，其降解的半衰期估计约为64小时。在孵育96小时的细胞中，无论后续有无骨化三醇培养，均观察到相同的降解速率（即半衰期约为64小时）。骨化三醇不影响总可溶性蛋白的降解速率。
