title: Enzymatic isomerization and epimerization of D-erythrose 4-phosphate and its quantitative analysis by gas chromatography/mass spectrometry.
abstract: An enzyme preparation from beef liver catalyzed the isomerization and epimerization of D-erythrose 4-phosphate to D-erythrulose 4-phosphate and D-threose 4-phosphate. The presence of D-erythrulose 4-phosphate and D-threose 4-phosphate was demonstrated by several analytical methods. After dephosphorylation, the presence of D-erythrulose and D-threose was confirmed by thin-layer chromatography, gas-liquid chromatography and an enzymatic method depending upon D-erythrulose reductase. The enzymatic products were also identified and simultaneously quantitated by a new procedure using gas chromatography/mass spectrometry. Each of three tetroses was distinguished by the combination of the reduction with sodium borodeuteride and the determination of relative intensities of the ion pairs m/z 379 and 380 of sugar tetritol trifluoroacetate. By gas chromatography/mass spectrometry, we observed that D-threose 4-phosphate was also converted into D-erythrulose 4-phosphate and D-erythrose 4-phosphate. At the equilibrium, about 90% of the tetrose 4-phosphate existed in the form of D-erythrulose 4-phosphate. On the basis of gas chromatography/mass spectrometric evidence together with gas chromatographic and thin-layer chromatographic patterns, it is suggested that the single enzyme of the beef liver catalyzed both reactions of isomerization and epimerization of aldotetrose 4-phosphate.
mesh_terms: D000818:Animals; D002417:Cattle; D008401:Gas Chromatography-Mass Spectrometry; D007535:Isomerases / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D019998:Racemases and Epimerases / Q000378:metabolism*; D013401:Sugar Alcohol Dehydrogenases; D013403:Sugar Phosphates / Q000032:analysis / Q000378:metabolism*
chemical_list: D013403:Sugar Phosphates; C026959:erythrose 4-phosphate; C042347:erythrulose 4-phosphate; D013401:Sugar Alcohol Dehydrogenases; C020117:D-erythrulose reductase; D007535:Isomerases; D019998:Racemases and Epimerases