A new isomerization reaction was developed to synthesize rare ketoses. D-tagatose, D-xylulose, and D-ribulose were obtained in the maximum yields of 24%, 38%, and 40%, respectively, from the corresponding aldoses, D-galactose, D-xylose, and D-ribose, by treating the aldoses with 80% (v/v) subcritical aqueous ethanol at 180°C. The maximum productivity of D-tagatose was ca. 80 g/(Lh). Increasing ...

Abstract Background Saussurea involucrata survives in extreme arctic conditions and is very cold-resistant. This species grows rocky, mountainous areas with elevations of 2400–4100 m, which are snow-covered year-round subject to freezing temperatures. S. ’s ability survive an low-temperature environment suggests that it has particularly high photosynthetic efficiency, providing a magnificent mo...

The slow, ordered, readily reversible binding of COZ and Mgl’ to ribulose bisphosphate carboxylase/oxygenase to form the active ternary enzyme-COz*Md+ complex has been studied at suboptimal COZ concentrations in the presence of various effectors. Sugar monophosphates, sugar bisphosphates, phosphate, and other anionic compounds either stimulated, inhibited, or had no effect on initial rates of c...

background chronic hypoxia causes apoptosis of cardiac myocytes, however, energy production by anaerobic glycolysis protects myocardium against hypoxia injuries. aldolase a is a well-characterised key enzyme of the glycolysis pathway. ghrelin, a 28-amino-acid peptide, synthesizes in the stomach and has protective roles in cardiovascular systems and also affects metabolic pathways. objectives th...

Two forms of the enzyme fructoseI ,6-bisphosphate aldolase (EC 4. I .2.13) are known, designated class I and class 11. The enzymes o f class I function by imine formation between the substrate and a catalytically essential lysine residue in the active site, which acts to stabilize the intermediate carbanion (for review, see [ I , 21). The enzymes of class I1 utilize a divalent metal ion to act ...

The aldolase catalytic cycle consists of a number of proton transfers that interconvert covalent enzyme intermediates. Glu-187 is a conserved amino acid that is located in the mammalian fructose-1,6-bisphosphate aldolase active site. Its central location, within hydrogen bonding distance of three other conserved active site residues: Lys-146, Glu-189, and Schiff base-forming Lys-229, makes it a...

OH OH Two main classes of aldolases are found in Nature. Type I aldolases activate the nucleophilic partner by forming an imine as an intermediate; this type of enzyme is found in animals and higher plants. Type II aldolases occur in microorganisms and they require R 2 to be a hydroxy group. These enzymes feature a Zn 2+ ion that promotes the reaction by forming a chelate with both the carbonyl...

Class I fructose-1,6-bisphosphate aldolases catalyze the interconversion between the enamine and iminium covalent enzymatic intermediates by stereospecific exchange of the pro(S) proton of the dihydroxyacetone-phosphate C3 carbon, an obligatory reaction step during substrate cleavage. To investigate the mechanism of stereospecific proton exchange, high resolution crystal structures of native an...