Plant Physiology 47:740-744 (1971)
© 1971 American Society of Plant Biologists
Articles
Solubilization and Separation of Uridine Diphospho-D-glucose: -(1 4) Glucan and Uridine Diphospho-D-glucose: -(1 3) Glucan Glucosyltransferases from Coleoptiles of Avena sativa1
C. M. Tsai and
W. Z. Hassid
a Department of Biochemistry, University of California, Berkeley, California 94720
The particulate glucan synthetase preparation isolated from a homogenate of oat coleoptiles at 4 C lost 65% of its original activity after 1 day when the UDP-D-glucose substrate concentration was 5 x 107M to 1.0 x 106M. Storage of the particulate enzyme at 20 C or in liquid nitrogen did not prevent the enzyme from losing its activity. Incorporation of 0.5% hovine serum albumin into the medium stabilized the particulate enzyme at 0 C for 6 days and for at least 2 weeks in liquid nitrogen.
When the particulate enzyme was treated with 8% digitonin, 40 to 50% of its activity appeared in the 100,000g supernatant fraction. The particulate and digitonin-solubilized enzyme preparations synthesized both -(1 4) and -(1 3) glucosyl linkages from UDP-D-glucose, but -(1 3) glucan was the main product at 1 x 103M UDP-D-glucose substrate. The activity of -(1 4) glucan synthetase was stimulated at least 10-fold in the presence of MgCl2. A separation of -(1 4) and -(1 3) glucan synthetase activities could be achieved at 1 x 103M UDP-D-glucose when the digitonin-solubilized enzyme was adsorbed on a hydroxylapatite gel and then eluted with concentrated potassium phosphate buffer. The results indicate that the particulate enzyme contains two enzymes, one responsible for the synthesis of -(1 4) and another -(1 3) linkages in the glucan or glucans synthesized from UDP-D-glucose.
1 This investigation was supported in part by Research Grant A-1418 from the National Institutes of Health, United States Public Health Service, and by Research Grant GB11819 from the National Science Foundation. Support of this work by the Agricultural Experiment Station is also acknowledged.
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