کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1179733 962795 2006 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Structural elements in dextran glucosidase responsible for high specificity to long chain substrate
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آنالیزی یا شیمی تجزیه
پیش نمایش صفحه اول مقاله
Structural elements in dextran glucosidase responsible for high specificity to long chain substrate
چکیده انگلیسی

Dextran glucosidase from Streptococcus mutans (SMDG) and Bacillus oligo-1,6-glucosidases, members of glycoside hydrolase family 13 enzymes, have the high sequence similarity. Each of them is specific to α-1,6-glucosidic linkage at the non-reducing end of substrate to liberate glucose. The activities toward long isomaltooligosaccharides were different in both enzymes, in which SMDG and oligo-1,6-glucosidase showed high and low activities, respectively. We determined the structural elements essential for high activity toward long-chain substrate. From conformational comparison between SMDG and B. cereus oligo-1,6-glucosidase (three-dimensional structure has been solved), Trp238 and short β → α loop 4 of SMDG were considered to contribute to the high activity to long-chain substrate. W238A had similar kcat/Km value for isomaltotriose to that for isomaltose, suggesting that the affinity of subsite +2 was decreased by Trp238 replacement. Trp238 mutants as well as the chimeric enzyme having longer β → α loop 4 of B. subtilis oligo-1,6-glucosidase showed lower preference for long-chain substrates, indicating that both Trp238 and short β → α loop 4 were important for high activity to long-chain substrates.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics - Volume 1764, Issue 4, April 2006, Pages 688–698
نویسندگان
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