Neisseria perflava amylosucrase: characterization of its product polysaccharide and a study of its inhibition by sucrose derivatives.
Neisseria perflava amylosucrase forms from sucrose a polysaccharide very similar to glycogen, except that a larger proportion of its D-glucosyl residues are in short branches. Iodine staining of samples taken during polysaccharide formation indicate that the initial product is less branched than that formed at longer times. This glycogen-like polysaccharide has an estimated molecular mass range of 1 MD to 20 MD. Sucrose derivatives modified at C-3 (3-deoxysucrose and alpha-D-allopyranosyl beta-D-fructofuranoside), C-6 (6-deoxysucrose and 6-deoxy-6-fluorosucrose), and both C-4 and C-6 (4,6-dideoxysucrose) were tested as inhibitors of amylosucrase. Derivatives modified at C-6 were potent competitive inhibitors, with Ki values of 6.2 +/- 0.3 mM (6-deoxysucrose) and 0.50 +/- 0.06 mM (6-deoxy-6-fluorosucrose). The KM value of sucrose is 26.5 +/- 4.6 mM. Sucrose derivatives modified at C-3 were not significantly inhibitory over the concentration range tested. 4,6-Dideoxysucrose gave an unusual, non-competitive inhibition, in that, increasing its concentration did not produce a commensurate increase in the level of inhibition, which instead appeared to approach a limit. None of these sucrose derivatives was a substrate for amylosucrase, nor were they glycosyl donors to maltotriose.
Tao
B Y
BY
Department of Chemical Engineering, Iowa State University, Ames 50011.
Reilly
P J
PJ
Robyt
J F
JF
D005964:Glucosyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D009343:Neisseria / Q000201:enzymology*; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D013329:Structure-Activity Relationship; D013395:Sucrose / Q000031:analogs & derivatives / Q000494:pharmacology
D011135:Polysaccharides, Bacterial; D013395:Sucrose; D005964:Glucosyltransferases; C019700:amylosucrase