Adenosine triphosphate (ATP) regeneration systems are essential for efficient biocatalytic phosphoryl transfer reactions. Polyphosphate kinase (PPK) is a versatile enzyme that can transfer phosphate groups among adenosine monophosphate (AMP), adenosine diphosphate (ADP), ATP, and polyphosphate (Poly P). Utilization of PPK is an attractive solution to address the problem of ATP regeneration due to its ability to use a variety of inexpensive and stable Poly P salts as phosphate group donors. This review comprehensively summarizes the structural characteristics and catalytic mechanisms of different types of PPKs, as well as the variations in enzyme activity, catalytic efficiency, stability, and coenzyme preference observed in PPKs from different sources. Moreover, recent advances in PPK-mediated ATP regeneration systems and protein engineering of wild-type PPK are summarized.
Adenosine Triphosphate/metabolism* ; Adenosine Monophosphate ; Polyphosphates/metabolism* ; Catalysis ; Regeneration

The energy metabolism of the brain has been measured in cat model using high performance liquid chromatography(HPLC). The experimental groups were divided into three according to the duration of ischemia. In 1- and 3-hour ischemia groups, recirculation had increased the ATP, UTP and GTP significantly to 39-49%, 53-57% and 39-62% of the sham control value respectively. Also in these groups, recirculation had increased adenylate energy charge(E.C.) to 75-82% of sham control value. Whereas there were slight increase in adenylate E.C. after recirculation in 5-hr ischemia group, with the remainders not increasing significantly. The Na+, K+-ATPase activities were not significant statistically among the groups. These results suggest that in order to prevent from the irreversible ischemic brain damage, restoration of blood flow must be accomplished within 3 hours from the onset of the acute focal ischemia in cat.
Adenosine Triphosphate ; Animals ; Brain ; Cats ; Chromatography, High Pressure Liquid ; Energy Metabolism* ; Guanosine Triphosphate ; Ischemia ; Uridine Triphosphate

Adenosine Triphosphate ; Mouth ; metabolism ; Receptors, Purinergic P2X ; metabolism

In order to clarify the cause of intracellular ATP dependency on Zn2+ blockade of KATP channels in pancreatic beta cells, we investigated the KATP channel activity during external Zn2+ application using voltage clamp technique. Cultured beta cells were used for patch-clamp experiment. When 3 mM glucose was applied in bath, KATP channel activity was increased transiently by externally applied Zn2+ in the cell-attached mode and was recoverable. The KATP channel activity was, however, consistently increased by Zn2+ application during the 0 mM glucose in bath. Inside-out mode, internally applied Zn2+ elicited no response on the KATP channels. Another divalent cation, Mn2+, didn't have any effect on the KATP channels. Therefore, This effect, so-called external glucose-dependency on Zn2+ blockade of the KATP channels, might be due to intracellular Zn2+ metabolism which induces ATP consumption. This appears to be a mechanism that the Zn2+ blockade of the KATP channels in the pancreatic beta cells depends on the intracellular ATP concentration.
Adenosine Triphosphate* ; Baths ; Glucose ; Insulin-Secreting Cells* ; KATP Channels* ; Metabolism

The study was designed to examine the effects of pretreatment with mannitol, methyl prednisolone and nimodipine on the acute focal cerebral ischemia in the cats of occlusion of the proximal part of the middle cerebral artery via the postorbital approach. The energy metabolisms of the brain was measured utilizing the high liquid performance chromatography in the brain tissues of cats. The experimental animals were seperated into 3 groups. group I: the sham control group. group II: the recirculation group. group III: the treatment group. There were significant increase in the ATP, GTP, UTP and E.C. levels in focal ischemic cerebral tissues of the treatment group when compared with the recirculation group. It is suggested that pretreatment with the combination of these drugs may prevent the ischemic damage from the acute focal cerebral ischemia by the maintenance of high energy metabolites. However further studies should determine the synergistic pharmacologic mechanisms in this therapeutic strategy.
Adenosine Triphosphate ; Animals ; Brain ; Brain Ischemia* ; Cats ; Chromatography ; Energy Metabolism ; Guanosine Triphosphate ; Mannitol ; Middle Cerebral Artery ; Nimodipine ; Prednisolone ; Uridine Triphosphate

The purpose of this study is to investigate the effect of methylprednisolone(M.P.) on the alterations of ATP, sum of adenosine nucleotides, adenylate energy charge(E.C.), glucose and lactate in the cats with acute focal ischemic cerebral edema. The acute occlusion of left middle cerebral artery(MCA) of forty cats for 1,3 and 5 hours respectively were accomplished by applying Heifetz clip through the transorbital approach operating microscope. Twelve cats were not recirculated as a untreated group, twelve cats were recirculated for 2 hours as a ecirculation group and twelve cats were recirculated for 2 hours and given M.P.(15mg/kg) at 30 minutes after occlusion initially, and then every one and a half hour as a treatment group. The experimental results are as follows. 1) In 1-hour untreated group, ATP was reduced to 34.0%, sum of adenosine nucleotides reduced to 72.2%, adenylate E.C. reduced to 60.6%, glucose reduced to 67.3% and lactate increased to 156.6% of the control value. In the recirculation group, ATP was reduced to 42.0%, sum of adenosine nucleotides reduced to 82.4%, adenylate E.C. reduced to 74.3%, glucose increased to 552.7% and lactate decreased to 79.8%. In the treatment group, ATP was increased to 143.9%, sum of adenosine nucleotides increased to 153.9%, adenylate E.C. decreased to 92.9%, glucose increased to 3334.5% and lactate decreased to 74.6%. 2) In 3-hour untreated group, ATP was decreased to 24.9%, sum of adenosine nucleotides reduced to 22.9%, adenylate E.C. reduced to 58.6%, glucose decreased to 45.5% and lactate increased to 161.3% of the control value. In the recirculation group, ATP reduced to 32.9%, sum of adenosine nucleotides reduced to 28.6%, adenylate E.C. reduced to 71.4%, glucose rose to 520.0% and lactate to 135.3% of the control value. In the treatment group, ATP reduced to 99.5%, sum of adenosine nucleotides increased to 103.5%, adenylate E.C. decreased to 84.3%, glucose rose to 1187.3% and lactate increased to 101.2%. 3) In 5-hour untreated group, ATP decreased to 5.3%, sum of adenosine nucleotides reduced to 9.0%, adenylate E.C. reduced to 58.6%, glucose decreased to 25.5% and lactate increased to 187.9%. In the recirculation group, ATP decreased to 4.4%, sum of adenosine nucleotides decreased to 5.8%, adenylate E.C. decreased to 57.1%. In the treatment group, ATP was reduced to 11.2%, sum of adenosine nucleotides and adenylate E.C. reduced to 70.0%, glucose rose to 103.6% and lactate to 157.2% of the control value. As the results shown above, the therapeutic beneficial effects of M.P. were observed in cats of 1 or 3-hour occlusion of MCA with 2-hour recirculation.
Adenosine ; Adenosine Triphosphate ; Animals ; Brain Edema ; Cats ; Energy Metabolism* ; Glucose ; Ischemia* ; Lactic Acid ; Methylprednisolone* ; Nucleotides

It is the purpose of this experimental study to investigate the alterations of the amount of adenosine nucleotides and adenylate energy charge in the acute focal cerebral ischemia of cats utilizing high performance liquid chromatography and to make a comparative study of protective effects of recirculation and combined therapy with mannitol, steroid and barbiturate. Acute focal cerebral ischemia in cats was induced by occlusion of the left middle cerebral artery through the postorbital technique. The experimental animals were divided into four groups according to the duration of occlusion time. The experimental results are obtained as follows: 1) In 1, 3 and 5 hour-occlusion groups, amount of adenosine triphosphate and summation of adenosine nucleotides decreased significantly to 21.4%, 5% & 0%, 44.0%, 29.9% & 10.8% of the sham control, respectively. Also in these groups adenylate energy charge decreased significantly to 62.7%, 38.7% and 30.7% of the sham control, respectively. It was suggested that the longer duration of occlusion time was, the more amount of adenosine triphosphate, summation of adenosine nucleotides and adenylate energy charge decreased significantly. 2) In 1 and 3 hour-occlusion groups, 2 hour-recirculation increased significantly amount of adenosine triphosphate and summation of adenosine nucleotides to 37.4% & 29.4%, and 62.1% & 58.3% of the sham control, respectively. Also in these groups recirculation increased significantly adenylate energy charge to 70.7% and 65.3% of the sham control, respectively. Whereas there was a slight increase of adenylate energy charge after recirculation in 5 hour-occlusion group, but not significant. 3) In the groups of recirculation following 5 hour-occlusion, pretreatment of combination of mannitol and steroid, or mannitol, steroid and barbiturate increased significantly amount of adenosine triphosphate, summation of adenosine nucleotides, and adenylate energy charge to 57.2% or 66.1%, 80.9% or 83.5% and 82.7% or 84.0% of sham control, respectively.
Adenosine ; Adenosine Triphosphate ; Animals ; Brain Ischemia ; Cats ; Chromatography, Liquid ; Mannitol ; Metabolism* ; Middle Cerebral Artery ; Nucleotides

Objective To observe the effect of excess oxygen supply for different time periods on the mitochondrial energy metabolism in alveolar epithelial type Ⅱ cells. Methods Rat RLE-6TN cells were assigned into a control group (21% O₂ for 4 h) and excess oxygen supply groups (95% O₂ for 1,2,3,and 4 h,res-pectively).The content of adenosine triphosphate (ATP),the activity of mitochondrial respiratory chain complex V,and the mitochondrial membrane potential were determined by luciferase assay,micro-assay,and fluorescent probe JC-1,respectively.Real-time fluorescence quantitative PCR was employed to determine the mRNA levels of NADH dehydrogenase subunit 1 (ND1),cytochrome b (Cytb),cytochrome C oxidase subunit I (COXI),and adenosine triphosphatase 6 (ATPase6) in the core subunits of mitochondrial respiratory chain complexes Ⅰ,Ⅲ,Ⅳ,and Ⅴ,respectively. Results Compared with the control group,excess oxygen supply for 1,2,3,and 4 h down-regulated the mRNA levels of ND1 (q=24.800,P<0.001;q=13.650,P<0.001;q=9.869,P<0.001;q=20.700,P<0.001),COXI (q=16.750,P<0.001;q=10.120,P<0.001;q=8.476,P<0.001;q=14.060,P<0.001),and ATPase6 (q=22.770,P<0.001;q=15.540,P<0.001;q=12.870,P<0.001;q=18.160,P<0.001).Moreover,excess oxygen supply for 1 h and 4 h decreased the ATPase activity (q=9.435,P<0.001;q=11.230,P<0.001) and ATP content (q=5.615,P=0.007;q=5.029,P=0.005).The excess oxygen supply for 2 h and 3 h did not cause significant changes in ATPase activity (q=0.156,P=0.914;q=3.197,P=0.116) and ATP content (q=0.859,P=0.557;q=1.273,P=0.652).There was no significant difference in mitochondrial membrane potential among the groups (F=0.303,P=0.869). Conclusion Short-term excess oxygen supply down-regulates the expression of the core subunits of mitochondrial respiratory chain complexes and reduces the activity of ATPase,leading to the energy metabolism disorder of alveolar epithelial type Ⅱ cells.
Animals ; Rats ; Energy Metabolism ; Adenosine Triphosphate ; Adenosine Triphosphatases ; RNA, Messenger ; Oxygen

The adenosine 5'-triphosphate (ATP)-binding cassette (ABC) transporter, IrtAB, plays a vital role in the replication and viability of Mycobacterium tuberculosis (Mtb), where its function is to import iron-loaded siderophores. Unusually, it adopts the canonical type IV exporter fold. Herein, we report the structure of unliganded Mtb IrtAB and its structure in complex with ATP, ADP, or ATP analogue (AMP-PNP) at resolutions ranging from 2.8 to 3.5 Å. The structure of IrtAB bound ATP-Mg2+ shows a "head-to-tail" dimer of nucleotide-binding domains (NBDs), a closed amphipathic cavity within the transmembrane domains (TMDs), and a metal ion liganded to three histidine residues of IrtA in the cavity. Cryo-electron microscopy (Cryo-EM) structures and ATP hydrolysis assays show that the NBD of IrtA has a higher affinity for nucleotides and increased ATPase activity compared with IrtB. Moreover, the metal ion located in the TM region of IrtA is critical for the stabilization of the conformation of IrtAB during the transport cycle. This study provides a structural basis to explain the ATP-driven conformational changes that occur in IrtAB.
Siderophores/metabolism* ; Iron/metabolism* ; Mycobacterium tuberculosis/metabolism* ; Cryoelectron Microscopy ; Adenosine Triphosphate/metabolism* ; ATP-Binding Cassette Transporters

Adenosine ; metabolism ; Adenosine Kinase ; metabolism ; Adenosine Triphosphate ; metabolism ; Animals ; Brain ; drug effects ; metabolism ; Diet, Carbohydrate-Restricted ; methods ; Diet, Ketogenic ; Energy Metabolism ; Epilepsy ; diet therapy ; metabolism ; Humans