Starch metabolism in Pseudomonas stutzeri. II. Purification and properties of a dextrin glycosyl-transferase (D-enzyme) and amylomaltase.
Amylomaltase and disproportionating enzyme (D-enzyme) were purified to homogeneity from cell-free extracts of Pseudomonas stutzeri using a six-step procedure. The presence of both glycosyltransferases in the same organism has not been reported before. Molecular weight determination by gel chromatography gave a value of 74,000 for the amylomaltase and 115 000 for the D-enzyme. Two subunits of different molecular weight were found in each enzyme as proved by sodium dodecyl sulfate-gel electrophoresis. The optimum pH of amylomaltase and D-enzyme activity is 7.6--7.7. Action of both glycosyltransferases on different maltodextrins showed that amylomaltase is most active with maltotetraose, and the Km value for this substrate is 7.1 mM. D-Enzyme catalyzed glucose release from maltose (Km = 8.3 mM) at a higher rate than from maltotriose and maltotetraose. With maltotriose as initial substrate, D-enzyme forms glucose, maltopentaose, maltoheptaose, maltononaose, maltoundecaose as major products. Amylomaltase acts on maltotriose, maltotetraose, and maltopentaose to form a series of homologous 1,4-alpha-glucans. No essential chain-lengthening reaction occurred with maltohexaose.
D005936:Glucans; D005964:Glucosyltransferases / Q000302:isolation & purification* / Q000378:metabolism; D006004:Glycogen Debranching Enzyme System; D007700:Kinetics; D008970:Molecular Weight; D011549:Pseudomonas / Q000378:metabolism*; D013213:Starch / Q000378:metabolism*; D013379:Substrate Specificity
D005936:Glucans; D006004:Glycogen Debranching Enzyme System; D013213:Starch; D005964:Glucosyltransferases; C020569:4 alpha-glucanotransferase