2922-69-2Relevant articles and documents
Reconstitution and biochemical characterization of a new pyridoxal-5′-phosphate biosynthetic pathway
Burns, Kristin E.,Xiang, Yun,Kinsland, Cynthia L.,McLafferty, Fred W.,Begley, Tadhg P.
, p. 3682 - 3683 (2005)
The substrates for Bacillus subtilis PLP synthase (YaaD and YaaE) are identified, and the first reconstitution of PLP biosynthesis using this pathway is described. Three partial reactions catalyzed by YaaD are also identified. Copyright
Vanadate tetramer as the inhibiting species in enzyme reactions in vitro and in vivo
Crans,Willging,Butler
, p. 427 - 432 (1990)
Tetrameric vanadate polyanion inhibits 6-phosphogluconate dehydrogenases from human, mammalian, yeast, and bacterial sources. The inhibition by a vanadate mixture containing monomer, dimer, and tetramer was determined by measuring the rates of 6-phosphogluconate oxidation and NADP (or NAD) reduction catalyzed by 6-phosphogluconate dehydrogenase. The inhibition by vanadate is competitive with respect to 6-phosphogluconate and mixed or noncompetitive with respect to NADP or NAD. 51V NMR spectroscopy was used to direcly correlate the inhibition of vanadate solutions to the vanadate tetramer. The measured inhibition constants with respect to 6-phosphogluconate for the tetramer are 0.078 mM for the human erythrocyte enzyme, 0.063 mM for the sheep liver enzyme, 0.013 mM for the yeast enzyme, and 0.24 mM for the Leuconostoc mesenteroides. The observed inhibition of 6-phosphogluconate dehydrogenase by vanadate tetramer is the first enzymatic activity observed of this polyanion. Our observations suggest the vanadate tetramer will be a potent inhibitor to other organic phosphate converting enzymes and preliminary results confirm this expectation. The vanadate tetramer may be an important species when considering the mechanism by which vanadium acts in biological systems in vitro and in vivo.
Stages of the formation of nonequivalence of active centers of transketolase from baker's yeast
Solovjeva, Olga N.,Selivanov, Vitaly A.,Orlov, Victor N.,Kochetov, German A.
, p. 122 - 129 (2019)
For baker's yeast transketolase (TK), cooperative binding of thiamine diphosphate (ThDP) and substrates in the transferase reaction is known. We show here that the differences in the properties of the active centers of TK are formed already upon the binding of Ca2+ in one of two initially identical subunits. When Ca2+ is bound in only one of the two active centers its affinity for the second decreases. The absence of a cation in the second active center decreases the affinity of ThDP to the first active center. Ca2+ binding increases the thermal stability of apo- and holoTK, i.e. changes the whole structure of the enzyme. Only in the presence of Ca2+, but not Mg2+, does the thermal stability of holoTK increase. In the one-substrate reaction in the presence of Ca2+, two Km are measured for the binding of xylulose-5-phosphate and hydroxypyruvate. For both substrates, Vmax of the first active center of holoTK, when it binds the substrate alone, is higher than of semiholoTK. When the substrate begins to bind also in the second active center, Vmax of both active centers decreases, which is explained by the previously shown flip-flop mechanism.
Facile Enzymatic Synthesis of Phosphorylated Ketopentoses
Wen, Liuqing,Huang, Kenneth,Liu, Yunpeng,Wang, Peng George
, p. 1649 - 1654 (2016/03/15)
An efficient and convenient platform for the facile synthesis of phosphorylated ketoses is described. All eight phosphorylated ketopentoses were produced using this platform starting from two common and inexpensive aldoses (d-xylose and l-arabinose) in more than 84% isolated yield (gram scale). In this method, reversible conversions (isomerization or epimerization) were accurately controlled toward the formation of desired ketose phosphates by targeted phosphorylation reactions catalyzed by substrate-specific kinases. The byproducts were selectively removed by silver nitrate precipitation avoiding the tedious and time-consuming separation of sugar phosphate from adenosine phosphates (ATP and ADP). Moreover, the described strategy can be expanded for the synthesis of other sugar phosphates.
Electrochemical oxidation of sugars at moderate potentials catalyzed by Rh porphyrins
Yamazaki, Shin-Ichi,Fujiwara, Naoko,Takeda, Sahori,Yasuda, Kazuaki
supporting information; experimental part, p. 3607 - 3609 (2010/08/07)
In this communication, we demonstrate that certain kinds of Rh porphyrins on carbon black can electrochemically oxidize aldose at low potentials. The onset potential was much lower than those with the other complex-based catalysts. A product analysis suggested that this reaction involves 2-electron oxidation of the aldehyde group.
