Uridine diphosphate glucose-sterol glucosyltransferase and nucleoside diphosphatase activities in etiolated pea seedlings.
1. UDP-glucose-sterol glucosyltransferase and nucleoside diphosphatases were isolated in a particulate fraction from 7-day-old etiolated pea seedlings. The glucosyltransferase and UDPase (uridine diphosphatase) are stimulated by Ca2+ cation, less so by Mg2+ cation, and inhibited by Zn2+. 2. Each activity has a pH optimum near 8. 3. The glucosyltransferase is specific for UDP-glucose as the glucosyl donor and is inhibited by UDP. Partial recovery from UDP inhibition is effected by preincubation of the enzyme. 4. Freeze-thaw treatment and subsequent sucrose-density-gradient centrifugation of the particulate fraction shows the glucosyltransferase to be widely distributed among cell fractions but to be most active in particles with a density of 1.15 g/ml. UDPase is most active in particulate material with a density of over 1.18 g/ml but an activity peak also appears at 1.15 g/ml. Of several nucleoside diphosphatase activities, UDPase activity is most enhanced by the freeze-thaw and sucrose-density-gradient-fractionation procedures. 5. Detergent treatment with 0.1% sodium deoxycholate allows the partial solubilization of the glucosyltransferase and UDPase. The two activities are similarly distributed between pellet and supernatant after high-speed centrifugation for two different time intervals. 6. A role for UDPase in the functioning of glucosylation reactions is discussed.
D017766:Acid Anhydride Hydrolases; D002118:Calcium / Q000494:pharmacology; D003624:Darkness; D003902:Detergents / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007887:Fabaceae / Q000201:enzymology; D005964:Glucosyltransferases / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010944:Plants / Q000201:enzymology*; D010946:Plants, Medicinal; D012265:Ribonucleotides / Q000494:pharmacology; D013261:Sterols; D014532:Uridine Diphosphate Glucose
D003902:Detergents; D012265:Ribonucleotides; D013261:Sterols; D005964:Glucosyltransferases; D010744:Phosphoric Monoester Hydrolases; D017766:Acid Anhydride Hydrolases; C023837:nucleoside-diphosphatase; D008274:Magnesium; D002118:Calcium; D014532:Uridine Diphosphate Glucose