Studies on Chrysanthemic Acid |
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Authors: | Masanao Matsui Yasuhiro Yamada |
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Institution: | Department of Agricultural Chemistry, The University of Tokyo, Tokyo |
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Abstract: | Ribose-5-phosphate ketol-isomerase, an enzyme isomerizing ribose-5-phosphate to ribulose-5-phosphate, is isolated from Candida utilis which is grown in a medium containing xylose. The enzyme is also purified by means of fractionation with ammonium sulfate, acetone, and by DEAE-cellulose column chromatography.The enzyme has its optimum pH at 7.5 and optimum temperature at 50°C.Michaelis-Menten constant for d-ribose-5-phosphate is 7.38 × 10?4 M and activation energy of the enzyme reaction is 10,525 calories.The enzyme activity is inhibited by p-CMB, EDTA and sodium pyrophosphate, and activated by the addition of magnesium ion.Extract of Candida utilis contains polyol: NAD oxidoreductase which catalyzes the conversion of polyols to the corresponding ketoses.By fractionation with ammonium sulfate and on DEAE-cellulose column chromatography, the purity of enzyme has been increased about 14-fold.The relatively high activity with both xylitol and sorbitol suggests that they may be the natural substances for the enzyme.Evidence suggests that this enzyme relates to the metabolism of d-xylose in Candida utilis. |
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