Expression of a fungal glucoamylase in transgenic rice seeds.
Glucoamylase, which catalyses the hydrolysis of the alpha-1,4 glycosidic bonds of starch, is an important industrial enzyme used in starch enzymatic saccharification. In this study, a glucoamylase gene from Aspergillus awamori, under the control of the promoter of seed storage protein Gt1, was introduced into rice by Agrobacterium-mediated transformation. Significant glucoamylase activity was detected specifically in the seeds but not other tissues of the transgenic rice lines. The highest enzymatic activity was found in the transgenic line Bg17-2, which was estimated to have about 500 units per gram of seeds (one unit is defined as the amount of enzyme that produces 1 micromol of reducing sugar in 1 min at 60 degrees C using soluble starch as substrate). The optimum pH for the activity of the rice produced enzyme is 5.0-5.5, and the optimum temperature is around 60 degrees C. One part of this transgenic glucoamylase rice seed flour fully converted 25 parts of corn starch pre-liquefied by an alpha-amylase also produced by a transgenic rice into glucose in 16 h incubation. This study suggests that this hydrolysis enzyme may substitute commercial fermentation enzymes for industrial starch conversion.
Xu
Xiaoli
X
Institute of Insect Sciences and National Key Laboratory of Rice Biology, School of Agriculture and Biotechnology, HuajiaChi Campus, Zhejiang University, Hangzhou 310029, China.
Huang
Jinming
J
Fang
Jun
J
Lin
Chaoyang
C
Cheng
Jiaan
J
Shen
Zhicheng
Z
D001230:Aspergillus / Q000201:enzymology*; D004789:Enzyme Activation; D020869:Gene Expression Profiling; D005087:Glucan 1,4-alpha-Glucosidase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction / Q000379:methods; D012639:Seeds / Q000235:genetics* / Q000378:metabolism; D013696:Temperature; D014170:Transformation, Genetic / Q000235:genetics
D005087:Glucan 1,4-alpha-Glucosidase