果糖二磷酸钠(1,6-二磷酸果糖,FDP)作为细胞内糖代谢的重要中间产物,能够调节糖代谢中若干酶的活性。作为一种分子水平上的药物,它被广泛用于治疗冠心病、心绞痛、心肌梗塞、脑梗塞和休克等疾病,并取得了满意的效果。近年来,在其他疾病的临床应用方面也有了新的进展。
化学性质果糖二磷酸钠是一种白色或类白色的结晶性粉末,易溶于水但在乙醇、丙酮和乙醚中几乎不溶。在生命活动中,它作为高能磷酸键的载体,参与ATP(三磷酸腺苷)的合成与分解过程。
生物活性果糖二磷酸钠是一种细胞保护性的天然糖磷酸盐,在心血管缺血、镰状细胞性贫血和哮喘的研究中有潜在的应用价值。通过刺激无氧糖酵解作用,它在缺血条件下能够产生三磷酸腺苷(ATP)。
靶点果糖二磷酸钠主要用于心血管系统疾病的治疗。
虽然原核生物6-磷酸果糖激酶(糖酵解的关键酶之一)的晶体结构已经有了近25年的时间,但对于更为复杂和高度调节的真核生物酶的结构信息仍然缺乏。本综述基于最近的晶体结构、动力学分析和定点突变数据,重点介绍真核生物6-磷酸果糖激酶的分子结构和变构调节的结构基础。
Phosphofructokinase-1 (Pfk) acts as the main control point of flux through glycolysis. It is involved in complex allosteric regulation and Pfk mutations have been linked to cancer development. Whereas the 3D structure and structural basis of allosteric regulation of prokaryotic Pfk has been studied in great detail, our knowledge about the molecular basis of the allosteric behaviour of the more complex mammalian Pfk is still very limited. To characterize the structural basis of allosteric regulation, the subunit interfaces and the functional consequences of modifications in Tarui's disease and cancer, we analysed the physiological homotetramer of human platelet Pfk at up to 2.67 Å resolution in two crystal forms. The crystallized enzyme is permanently activated by a deletion of the 22 C-terminal residues. Complex structures with ADP and fructose-6-phosphate (F6P) and with ATP suggest a role of three aspartates in the deprotonation of the OH-nucleophile of F6P and in the co-ordination of the catalytic magnesium ion. Changes at the dimer interface, including an asymmetry observed in both crystal forms, are the primary mechanism of allosteric regulation of Pfk by influencing the F6P-binding site. Whereas the nature of this conformational switch appears to be largely conserved in bacterial, yeast and mammalian Pfk, initiation of these changes differs significantly in eukaryotic Pfk.
Nucleotide sequence analysis of the Escherichia coli chromosomal DNA inserted in the plasmid pLC33-5 of the Clarke and Carbon library [Clarke & Carbon (1976) Cell 9, 91-99] revealed the existence of the gene, fda, encoding the Class II (metal-dependent) fructose 1,6-bisphosphate aldolase of E. coli. The primary structure of the polypeptide chain inferred from the DNA sequence of the fda gene comprises 359 amino acids, including the initiating methionine residue, from which an Mr of 39,146 could be calculated. This value is in good agreement with that of 40,000 estimated from sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the purified dimeric enzyme. The amino acid sequence of the Class II aldolase from E. coli showed no homology with the known amino acid sequences of Class I (imine-forming) fructose 1,6-bisphosphate aldolases from a wide variety of sources. On the other hand, there was obvious homology with the N-terminal sequence of 40 residues already established for the Class II fructose 1,6-bisphosphate aldolase of Saccharomyces cerevisiae. These Class II aldolases, one from a prokaryote and one from a eukaryote, evidently are structurally and evolutionarily related. A 1029 bp-fragment of DNA incorporating the fda gene was excised from plasmid pLC33-5 by digestion with restriction endonuclease HaeIII and subcloned into the expression plasmid pKK223-3, where the gene came under the control of the tac promoter. When grown in the presence of the inducer isopropyl-beta-D-thiogalactopyranoside, E. coli JM101 cells transformed with this recombinant expression plasmid generated the Class II fructose 1,6-bisphosphate aldolase as approx. 70% of their soluble protein. This unusually high expression of an E. coli gene should greatly facilitate purification of the enzyme for any future structural or mechanistic studies.