Histidine glucose phosphates

Interestingly, however, the mechanisms of the two phosphate hydrolysis reactions in steps 9 and 11 are not the same. In step 9, water is the nucleophile, but in the glucose 6-phosphate reaction of step 11, a histidine residue on the enzyme attacks phosphorus, giving a phosphoryl enzyme intermediate that subsequently reacts with water. 

P histidine-containing protein + D-glucitol phosphate S phosphohistidinoprotein -I- D-glucose <1> (<1> enzyme II complex [1])... 

Additional information < >(< > not inhibitory AMP, ADP, ATP, GMP, GDP, GTP, cAMP, cGMP, acetyl-CoA, acetyl phosphate, glucose 6-phosphate, glucose 1-phosphate, fructose 1,6-diphosphate, t-histidine, o-histidine [14])... 

Nordlie and Lygre (118, 132) have carried out detailed pH kinetic studies of PPi-glucose phosphotransferase, CDP-glucose phosphotransferase, and glucose-6-P phosphohydrolase activities with partially purified rat liver enzyme preparations, and they have concluded, on the basis of sharp, unit-changes in slopes of Dixon (133) plots of pKm for phosphate substrates vs. pH near 6.5, that enzyme-bound histidine may participate directly in the catalytic process. Values of Km for glucose were unaffected by reaction mixture pH Km values and relative Vmax values calculated for infinite concentrations of all substrates are tabulated in Table IX. 

The glucose-l-phosphatase from E. coli hydrolyzes phytate as well as glucose-1-phosphate. This enzyme is a member of the histidine acid phosphatase family (Lee et al., 2003). Glucose-l-phosphatase cleaves only the 3-phosphate from phytate, and no further hydrolysis takes place. It is the only phosphatase... 

Phosphatases specific for such substrates as glucose-6-phosphate, fructose-l,6-bisphosphate, and phospho-glycolate help to drive metabolic cycles (Chapter 17). The 335-residue fructose-1,6-bisphosphatase associates to form a tetramer with D2 symmetry. ° The allosteric enzyme exists in two conformational states (see Chapter 11). Activity is dependent upon Mg + or other suitable divalent cation, e.g., Mn or Zn, and is further enhanced by K+ or NH3. While the dimetal sites depicted in Figs. 12-23 and 12-24 are quite rigid and undergo little change upon formation of complexes with substrates or products, the active site of fructose-1,6-bisphosphatase is more flexible. There are three metal-binding sites but they contain no histidine side chains and have been seen clearly only in a product complex. Perhaps because of the need for... 

Synthesis.—Comprehensive reviews on glycosyl esters of nucleoside pyrc>-phosphates and teichoic acids have appeared in the past year as have details of the preparation of xylulose-5-phosphate using transketolase. Phosphorylation of glucose by inorganic phosphate in the presence of histidine occurs under simulated primitive earth conditions and the reactive species is probably an iST-phosphorylated histidine. Phosphorylation of sugars by heating them with 100% phosphoric acid in vacuo is a novel experimental... 

The usual kidney storage solutions use an imperme-ant solute, such as phosphate, lactobionate, glucose, sucrose or raffinose. There is less agreement about the need for other minor components used to minimize acidosis or oxidative reperfusion injury, or enhance regeneration following revascularization. At present, the best known solutions are University of Wisconsin (UW), histidine-tryptophan ketoglu-tarate (HTK, Custodiol ) or Celsior . 

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