Characterization of a novel debranching enzyme from Nostoc punctiforme possessing a high specificity for long branched chains.
A novel debranching enzyme from Nostoc punctiforme PCC73102 (NPDE) exhibits hydrolysis activity toward both alpha-(1,6)- and alpha-(1,4)-glucosidic linkages. The action patterns of NPDE revealed that branched chains are released first, and the resulting maltooligosaccharides are then hydrolyzed. Analysis of the reaction with maltooligosaccharide substrates labeled with (14)C-glucose at the reducing end shows that NPDE specifically liberates glucose from the reducing end. Kinetic analyses showed that the hydrolytic activity of NPDE is greatly affected by the length of the substrate. The catalytic efficiency of NPDE increased considerably upon using substrates that can occupy at least eight glycone subsites such as maltononaose and maltooctaosyl-alpha-(1,6)-beta-cyclodextrin. These results imply that NPDE has a unique subsite structure consisting of -8 to +1 subsites. Given its unique subsite structure, side chains shorter than maltooctaose in amylopectin were resistant to hydrolysis by NPDE, and the population of longer side chains was reduced.
Choi
Ji-Hye
JH
Center for Agricultural Biomaterials and Department of Food Science and Biotechnology, Seoul National University, Seoul 151-921, Republic of Korea.
Lee
Heeseob
H
Kim
Young-Wan
YW
Park
Jong-Tae
JT
Woo
Eui-Jeon
EJ
Kim
Myo-Jeong
MJ
Lee
Byong-Hoon
BH
Park
Kwan-Hwa
KH
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002384:Catalysis; D006004:Glycogen Debranching Enzyme System / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D008969:Molecular Sequence Data; D046937:Nostoc / Q000201:enzymology*; D011134:Polysaccharides / Q000378:metabolism*; D013379:Substrate Specificity; D047392:beta-Cyclodextrins / Q000378:metabolism*
D001426:Bacterial Proteins; D006004:Glycogen Debranching Enzyme System; D011134:Polysaccharides; D047392:beta-Cyclodextrins; C008315:maltodextrin