Steady-state inhibitory kinetic studies on the ligand binding modes of Aspergillus niger glucoamylase.
Inhibitory activities of 1-deoxynojirimycin and gluconolactone on Aspergillus niger glucoamylase were studied in relation to the subsite structure of the enzyme. Although both of these inhibitors are considered to bind at subsite 1 of the enzyme active site, 1-deoxynojirimycin showed competitive type inhibition but gluconolactone was a mixed type (or noncompetitive type) inhibitor for the hydrolysis of p-nitrophenyl alpha-D-glucoside. The former type of inhibition suggested that the main binding mode of the substrate was productive, but the latter, nonproductive. A possible way of explaining these apparent inconsistent results is to assume that the main binding mode of the substrate is productive and gluconolactone forms a nonproductive ternary complex with the enzyme and the substrate.
Tanaka
A
A
Faculty of Bioresources, Mie University, Japan. akiyoshi@bio.mie-u.ac.jp
Ohya
M
M
Yamamoto
T
T
Nakagawa
C
C
Tsuji
T
T
Senoo
K
K
Obata
H
H
D017485:1-Deoxynojirimycin / Q000494:pharmacology; D001234:Aspergillus niger / Q000201:enzymology*; D001667:Binding, Competitive; D020134:Catalytic Domain; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005087:Glucan 1,4-alpha-Glucosidase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D005942:Gluconates / Q000494:pharmacology; D005960:Glucosides / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D007783:Lactones; D008024:Ligands; D013379:Substrate Specificity
D004791:Enzyme Inhibitors; D005942:Gluconates; D005960:Glucosides; D007783:Lactones; D008024:Ligands; D017485:1-Deoxynojirimycin; C019502:4-nitrophenyl alpha-glucoside; D005087:Glucan 1,4-alpha-Glucosidase; C010730:beta-glucono-1,5-lactone