Enzymatic synthesis and properties of highly branched rice starch amylose and amylopectin cluster.
We enzymatically modified rice starch to produce highly branched amylopectin and amylose and analyzed the resulting structural changes. To prepare the highly branched amylopectin cluster (HBAPC), we first treated waxy rice starch with Thermus scotoductus alpha-glucanotransferase (TSalphaGT), followed by treatment with Bacillus stearothermophilus maltogenic amylase (BSMA). Highly branched amylose (HBA) was prepared by incubating amylose with Bacillus subtilis 168 branching enzyme (BBE) and subsequently treating it with BSMA. The molecular weight of TSalphaGT-treated waxy rice starch was reduced from 8.9 x 10(8) to 1.2 x 10(5) Da, indicating that the alpha-1,4 glucosidic linkage of the segment between amylopectin clusters was hydrolyzed. Analysis of the amylopectin cluster side chains revealed that a rearrangement in the side-chain length distribution occurred. Furthermore, HBAPC and HBA were found to contain significant numbers of branched maltooligosaccharide side chains. In short, amylopectin molecules of waxy rice starch were hydrolyzed into amylopectin clusters by TSalphaGT in the enzymatic modification process, and then further branched by transglycosylation using BSMA. HBAPC and HBA showed higher water solubility and stability against retrogradation than amylopectin clusters or branched amylose. The hydrolysis rates of HBAPC and HBA by glucoamylase and alpha-amylase greatly decreased. The k cat/ K m value of glucoamylase acting on the amylopectin cluster was 45.94 s(-1)(mg/mL)(-1) and that for glucoamylase acting on HBAPC was 11.10 s(-1)(mg/mL)(-1), indicating that HBAPC was 4-fold less susceptible to glucoamylase. The k cat/ K m value for HBA was 15.90 s(-1)(mg/mL)(-1), or about three times less than that for branched amylose. The k cat/ K m values of porcine pancreatic alpha-amylase for HBAPC and HBA were 496 and 588 s(-1)(mg/mL)(-1), respectively, indicating that HBA and HBAPC are less susceptible to hydrolysis by glucoamylase and alpha-amylase. HBAPC and HBA show potential as novel glucan polymers with low digestibility and high water solubility.
Lee
Chang-Kyu
CK
Center for Agricultural Biomaterials and Department of Agricultural Biotechnology, Seoul National University, Gwanak-Gu, Seoul, Korea.
Le
Quang-Tri
QT
Kim
Yung-Hee
YH
Shim
Jae-Hoon
JH
Lee
Seung-Jae
SJ
Park
Jin-Hee
JH
Lee
Kang-Pyo
KP
Song
Sang-Hoon
SH
Auh
Joong Hyuck
JH
Lee
Sung-Joon
SJ
Park
Kwan-Hwa
KH
D015061:1,4-alpha-Glucan Branching Enzyme / Q000378:metabolism; D000687:Amylopectin / Q000096:biosynthesis* / Q000737:chemistry; D000688:Amylose / Q000096:biosynthesis* / Q000737:chemistry; D001412:Bacillus subtilis / Q000201:enzymology; D001411:Geobacillus stearothermophilus / Q000201:enzymology; D006004:Glycogen Debranching Enzyme System / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D012275:Oryza / Q000737:chemistry*; D013213:Starch / Q000737:chemistry*; D013824:Thermus / Q000201:enzymology
D006004:Glycogen Debranching Enzyme System; D013213:Starch; D000688:Amylose; D000687:Amylopectin; D015061:1,4-alpha-Glucan Branching Enzyme; C020569:4 alpha-glucanotransferase; D006026:Glycoside Hydrolases; C120909:glucan 1,4-alpha-maltohydrolase